Methods for Treating Depressive Symptoms

ABSTRACT

The present application relates methods for treating a depressive symptom comprising administering an effective amount of a μ opioid receptor agonist or a pharmaceutically acceptable salt thereof to a subject in need thereof. Non-limiting examples of such agonist include the compounds of Formulas I, II, III, and IV, as well as the compounds of Table A.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 61/827,295, filed May 24, 2013, and U.S. Provisional ApplicationSer. No. 61/827,317, filed May 24, 2013, the contents of which areincorporated herein by reference in their entireties.

BACKGROUND

Depression (also known as depressive disorders or depressive symptoms)includes common but serious disorders of the brain characterized bycombinations of signs and symptoms that may include feelings ofhopelessness, guilt, worthlessness, and/or sadness alongside changes insleep and/or eating patterns. While complex depressive disorders arethought to be caused by multiple factors, it is widely accepted thatthese disorders generally have a neurochemical component. Currenttreatment regimens often consist of a combination of psychotherapy andone or more medications to regulate neurotransmitters such as dopamine,serotonin and norepinephrine.

Current pharmacological methods of treatment for depressive disorderscan be efficacious, but they often have significant drawbacks. Manyanti-depressants have a latency period of two to three weeks, a delaythat can be life-threatening to a patient who is depressed. After thisinitial period, if a chosen therapeutic shows little or no effect on thesymptoms of the patient, the treating physician may alter thetherapeutic regimen by increasing the dosage of the chosen drug or byrecommending an entirely new compound. Even after a medication provesefficacious, the patient may suffer side effects such as dizziness,weight gain, and a loss of libido. The patient may also develop atolerance to the drug, leading them to take ever-increasing doses inorder to achieve similar results. In certain cases, chemical dependencemay also develop, leading to potential abuse and, in the case of abruptdiscontinuation, major withdrawal (including the risk of grand malseizures and death).

While certain treatments for depressive disorders do exist, manycommonly used therapeutics suffer from significant drawbacks includinginefficacy, latency periods, tolerance, and chemical dependence. Thereis therefore an urgent need for new and improved methods of treatmentfor these disorders that may be used alone or in conjunction withexisting therapeutic modalities.

SUMMARY OF THE INVENTION

Provided herein are methods for treating depressive symptoms comprisingadministering to a subject in need thereof a μ opioid receptor agonist,e.g., a compound of Formula I, II, III, or IV, or Table A.

In one aspect, provided herein is a method of treating a depressivesymptom in a subject in need thereof, which comprises administering tothe subject an effective amount of a μ opioid receptor agonist thatexhibits an Emax of 5% to 45% in a GTPγS binding assay. In oneembodiment, the Emax is 15% to 35% in a GTPγS binding assay. In anotherembodiment, said agonist has a low risk of opioid dependence, opioidaddiction, and/or symptoms of opioid withdrawal.

In another aspect, provided herein is a method of treating a depressivesymptom in a subject in need thereof, which comprises administering tothe subject an effective amount of a compound that exhibits a maximaldopamine efflux in the nucleus accumbens of 125% to 300% over base linein a rat. In particular embodiments, the compound exhibits a maximaldopamine efflux in the nucleus accumbens of 200% to 300% over base linein a rat.

In another aspect, provided herein is a method of treating a depressivesymptom in a subject in need thereof, which comprises administering tothe subject an effective amount of a compound that does not attenuatethermal pain in a rodent hot plate model when administered at a dose ofat least 1 mg/kg. In one embodiment, the compound does not attenuatethermal pain in a rodent hot plate model when administered at a dose ofat least 3 mg/kg. In another embodiment, the compound does not attenuatethermal pain in a rodent hot plate model when administered at a dose of10 mg/kg.

In still another embodiment, provided herein is a method of treating adepressive symptom in a subject comprising administering to the subjecta compound of Formula I:

or a pharmaceutically acceptable salt thereof, wherein:

R₁ is cyclobutyl,

R₂ is H, hydroxyl, or methoxy; and

R₃ and R₄ are each, independently, H, hydroxyl, or NR₅R₆, wherein R₅ andR₆ are each independently H, alkyl or substituted acyl, oralternatively, R₃ and R₄, together with the carbon atom to which theyare attached, form C═O or C═CH₂.

In one embodiment of Formula I, substituted acyl is defined as follows:

wherein R₁₁ is linear or branched C₁-C₆ alkyl; R₁₂ is halo, C₁-C₆ alkyl,or C₁-C₆ alkoxy; and R₁₃ is aryl or heteroaryl. In one embodiment ofFormula (IV), R₁ is cyclopropyl.

In particular embodiments, the compound of Formula I is:

In another aspect, provided herein is a method of treating a depressivesymptom in a subject comprising administering to the subject a compoundof Formula II:

or a pharmaceutically acceptable salt thereof, wherein:

R₁ is C₁-C₆ alkyl, C₂-C₆ alkenyl, cycloalkyl, heterocyclyl,hydroxyalkyl, or alkoxyalkyl;

R_(1a) is H or methyl;

R₂ and R₃ are each methyl, or alternatively, R₂ and R₃, together withthe carbon atoms to which they are attached, form a 6-memberedunsubstituted carbocyclic ring;

when

is a single bond, R₄ is H; and

when

is a double bond, R₄ is O.

In particular embodiment, the compound of Formula II is:

Also provided herein is a method of treating a depressive symptom in asubject comprising administering to the subject a compound of FormulaIII:

or a pharmaceutically acceptable salt thereof, wherein:

R₁ is C₁-C₆ alkyl, C₂-C₆ alkenyl, aryl, cycloalkyl, heterocyclyl,benzyl, hydroxyalkyl, or alkoxyalkyl;

R_(1a) is H or methyl;

R₂ and R₃ are each H, methyl, or ethyl, or alternatively, R₂ and R₃,together with the carbon atoms to which they are attached, form a6-membered unsubstituted carbocyclic ring or carbonyl-substitutedcarbocyclic ring;

R₄ and R₅ are each, independently, H, hydroxyl, or C₁-C₆ alkyl;

R₆ is unsubstituted or substituted C₆-C₁₀ aryl, or substituted orunsubstituted heteroaryl comprising one or two 5- or 6-membered ringsand 1-4 heteroatoms selected from N, O and S; and

R₇ and R₈ are each, independently, H or hydroxyl.

In particular embodiment, the compound of Formula III is:

Furthermore, provided herein is a method of treating a depressivesymptom in a subject comprising administering to the subject a compoundof Formula IV:

or a pharmaceutically acceptable salt thereof, wherein:

R₁ is C₁-C₆ alkyl, C₂-C₆ alkenyl, aryl, cycloalkyl, heterocyclyl,benzyl, hydroxyalkyl, or alkoxyalkyl;

R_(1a) is H or methyl;

R₂ is H, hydroxyl, or methoxy; and

R₃ and R₄ are each methyl, or alternatively, R₃ and R₄, together withthe carbon atoms to which they are attached, form a 6-memberedunsubstituted carbocyclic ring.

In certain embodiment, the compound of Formula IV is:

In yet another aspect, provided herein is a method of treating adepressive symptom in a subject comprising administering to the subjecta compound selected from:

or a pharmaceutically acceptable salt thereof.

In certain embodiments of the methods disclosed herein, the compound isa μ opioid receptor agonist that exhibits an Emax of 5% to 45% in aGTPγS binding assay. In particular embodiments, the Emax is 15% to 35%in a GTPγS binding assay. In other embodiments, said agonist has a lowrisk of opioid dependence, opioid addiction, and/or symptoms of opioidwithdrawal.

In other embodiments of the methods, the compound exhibits a maximaldopamine efflux in the nucleus accumbens of 125% to 300% over base linein a rat. In particular embodiments, the compound has a maximal dopamineefflux in the nucleus accumbens of 200% to 300% over base line in a rat.

In still other embodiments, the compound of the methods provided hereindoes not attenuate thermal pain in a rodent hot plate model whenadministered at a dose of at least 1 mg/kg. In particular embodiments,the compound does not attenuate thermal pain in a rodent hot plate modelwhen administered at a dose of at least 3 mg/kg. In other embodiments,the compound does not attenuate thermal pain in a rodent hot plate modelwhen administered at a dose of 10 mg/kg.

In preferred embodiments of the methods provided herein, the subject isa human.

In certain embodiments of the methods provided herein, the depressivesymptom is depressed mood, loss of pleasure, loss of appetite, sleepdisturbance, psychomotor changes, fatigue, and/or post-partumdepression.

In other embodiments, the depressive symptom is associated with a mentalcondition, wherein the mental condition is schizoaffective disorder,and/or seasonal affective disorder.

In still other embodiments, the depressive symptom is acute stressdisorder, adjustment disorders with depressed mood, Asperger syndrome,attention deficit, bereavement, bipolar I disorder, bipolar II disorder,borderline and personality disorder, cyclothymia and dysthymia,depression such as major depressive disorder (MDD) andtreatment-resistant disorder (TRD), Dysthymic disorder, hyperactivitydisorder, impulse control disorder, mixed mania, obsessive-compulsivepersonality disorder (OCD), paranoid, post-traumatic stress disorder,seasonal affective disorder, self-injury separation, sleep disorder,substance-induced mood disorder, Tourette syndrome and tic disorder,and/or Trichotillomania.

In other embodiments, the depressive symptom is an anxiety disorder,wherein the anxiety disorder is generalized anxiety disorder, panic,agoraphobia, acute stress, and/or post-traumatic stress disorder.

In still other embodiments of the treatment methods, the depressivesymptom is associated with chronic or recurrent depression.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the results of experiments measuring the antinociceptiveeffects of Compound A, either alone or in combination with morphine,using a rat hot plate assay.

FIG. 2 depicts the results of experiments measuring the antinociceptiveeffects of Compound A, or buprenorphine using a rat hot plate assay.

FIG. 3 depicts the results of in vivo microdialysis experimentsmeasuring dopamine release in the rat nucleus accumbens induced byCompound A and buprenorphine.

FIG. 4 depicts the results of experiments measuring the antinociceptiveeffects of morphine, Compound B, Compound C, Compound D and Compound E,using a rat hot plate assay.

FIG. 5 depicts the results of in vivo microdialysis experimentsmeasuring dopamine release in the rat nucleus accumbens induced bydifferent doses of Compound B.

FIG. 6 depicts the results of in vivo microdialysis experimentsmeasuring dopamine release in the rat nucleus accumbens induced bydifferent doses of Compound C.

FIG. 7 depicts the results of in vivo microdialysis experimentsmeasuring dopamine release in the rat nucleus accumbens induced bydifferent doses of Compound D.

FIG. 8 depicts the results of in vivo microdialysis experimentsmeasuring dopamine release in the rat nucleus accumbens induced bydifferent doses of Compound E.

FIG. 9 depicts the results of in vivo Forced Swim Test measuringreduction of immobility in rats induced by different doses of CompoundA, B or C.

DETAILED DESCRIPTION Methods of Treatment

The compounds of Formulas (I), (II), (III), (IV), and Table A, providedherein, are particularly suitable for treating a depressive symptom. Thedepressive symptom can be depressed mood, loss of pleasure, loss ofappetite, sleep disturbance, psychomotor changes, fatigue, and/orpost-partum depression. The depressive symptom can be associated with amental condition, wherein the mental condition is schizoaffectivedisorder, and/or seasonal affective disorder.

Furthermore, the depressive symptom can be acute stress disorder,adjustment disorders with depressed mood, Asperger syndrome, attentiondeficit, bereavement, bipolar I disorder, bipolar II disorder,borderline and personality disorder, cyclothymia and dysthymia,depression such as major depressive disorder (MDD) andtreatment-resistant disorder (TRD), Dysthymic disorder, hyperactivitydisorder, impulse control disorder, mixed mania, obsessive-compulsivepersonality disorder (OCD), paranoid, post-traumatic stress disorder,seasonal affective disorder, self-injury separation, sleep disorder,substance-induced mood disorder, Tourette syndrome and tic disorder,and/or Trichotillomania.

The depressive symptom can also be an anxiety disorder, wherein theanxiety disorder is generalized anxiety disorder, panic, agoraphobia,acute stress, and/or post-traumatic stress disorder.

The depressive symptom can be associated with chronic or recurrentdepression.

Accordingly, provided herein are methods of treating depressive symptomsin a subject in need thereof, comprising administering to the subject acompound, or a pharmaceutically acceptable salt thereof, of Formulas(I), (II), (III), or (IV), or Table A.

It has been discovered that Emax value in a GTPγS binding assay can beused to select a μ opioid receptor agonists for the treatment of adepressive symptom. In particular, it has been discovered that compoundswith an Emax of 5% to 45% in a GTPγS binding assay are especiallysuitable for treating depressive symptoms. Thus, in one aspect, providedherein is a method of treating a depressive symptom in a subject in needthereof comprising administering to the subject an effective amount of aμ opioid receptor agonist that exhibits an Emax of 5% to 45% (e.g., 5,10, 15, 20, 25, 30, 35, 40, or 45%) in a GTPγS binding assay. In aparticular embodiment, the Emax of the agonist is 15% to 35% in a GTPγSbinding assay. In another embodiment, the agonist has a low risk ofopioid dependence, opioid addiction and/or symptoms of opioidwithdrawal. Non-limiting examples of such agonist include the compoundsof Formulas I, II, III and IV, as well as the compounds of Table A.

It has also been discovered that a compound that exhibits a maximaldopamine efflux in the nucleus accumbens in a rat of 125% to 300% overbase line is particularly suitable for treatment of depressive symptoms.Thus, in another aspect, provided herein is a method of treating adepressive symptom in a subject in need thereof comprising administeringto the subject an effective amount of a compound that exhibits a maximaldopamine efflux in the nucleus accumbens in a rat of 125% to 300% (e.g.,125, 150, 175, 200, 225, 250, 275, or 300%) over base line. In aparticular embodiment, the maximal dopamine efflux in the nucleusaccumbens in a rat is 200% to 300% over base line. In anotherembodiment, the compound has a low risk of opioid dependence, opioidaddiction and/or symptoms of opioid withdrawal.

Non-limiting examples of such compound include the compounds of FormulasI, II, III and IV, as well as the compounds of Table A.

In still another aspect, provided herein is a method of treating adepressive symptom in a subject in need thereof comprising administeringto the subject an effective amount of a compound that does not attenuatethermal pain in a rodent hot plate model when administered at a dose ofat least 1 mg/kg (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 mg/kg). In oneembodiment, the compound does not attenuate thermal pain in a rodent hotplate model when administered at a dose of 1-10 mg/kg (e.g., 1, 2, 3, 4,5, 6, 7, 8, 9, or 10 mg/kg). In one embodiment, the compound does notattenuate thermal pain in a rodent hot plate model when administered ata dose of at least 3 mg/kg. In another embodiment, the compound does notattenuate thermal pain in a rodent hot plate model when administered ata dose of 10 mg/kg. In still another embodiment, the compound has a lowrisk of opioid dependence, opioid addiction and or symptoms of opioidwithdrawal. Non-limiting examples of such compound include the compoundsof Formulas I, II, III and IV, as well as the compounds of Table A.

In one aspect, provided herein is a method of treating a depressivesymptom in a subject in need thereof comprising administering to thesubject a compound of Formula I:

or a pharmaceutically acceptable salt thereof, wherein:

R₁ is cyclobutyl,

R₂ is H, hydroxyl, or methoxy; and

R₃ and R₄ are each, independently, H hydroxyl, or NR₅R₆, wherein R₅ andR₆ are each independently H, alkyl or optionally substituted acyl, oralternatively, R₃ and R₄, together with the carbon atom to which theyare attached, form C═O or C═CH₂.

In one embodiment, the substituted acyl is defined as follows:

wherein R₁₁ is linear or branched C₁-C₆ alkyl; R₁₂ is halo, C₁-C₆ alkyl,or C₁-C₆ alkoxy; and R₁₃ is aryl or heteroaryl. In one embodiment ofFormula (IV), R₁ is cyclopropyl.

In another embodiment, the compound of Formula I is

In another aspect, provided herein is a method of treating a depressivesymptom in a subject in need thereof comprising administering to thesubject a compound of Formula II:

or a pharmaceutically acceptable salt thereof, wherein:

R₁ is C₁-C₆ alkyl, C₂-C₆ alkenyl, cycloalkyl, heterocyclyl,hydroxyalkyl, or alkoxyalkyl;

R_(1a) is H or methyl;

R₂ and R₃ are each methyl, or alternatively, R₂ and R₃, together withthe carbon atoms to which they are attached, form a 6-memberedunsubstituted carbocyclic ring;

when

is a single bond, R₄ is H; and

when

is a double bond, R₄ is O.

In one embodiment, the compound of Formula II is:

In still another aspect, provided herein is a method of treating adepressive symptom in a subject in need thereof comprising administeringto the subject a compound of Formula III:

or a pharmaceutically acceptable salt thereof, wherein:

R₁ is C₁-C₆ alkyl, C₂-C₆ alkenyl, aryl, cycloalkyl, heterocyclyl,benzyl, hydroxyalkyl, or alkoxyalkyl;

R_(1a) is H or methyl;

R₂ and R₃ are each H, methyl, or ethyl, or alternatively, R₂ and R₃,together with the carbon atoms to which they are attached, form a6-membered unsubstituted carbocyclic ring or carbonyl-substitutedcarbocyclic ring;

R₄ and R₅ are each, independently, H, hydroxyl, or C₁-C₆ alkyl;

R₆ is unsubstituted or substituted C₆-C₁₀ aryl, or substituted orunsubstituted heteroaryl comprising one or two 5- or 6-membered ringsand 1-4 heteroatoms selected from N, O and S; and

R₇ and R₈ are each, independently, H or hydroxyl.

In one embodiment, the compound of Formula III is:

In another aspect, provided herein is a method of treating a depressivesymptom in a subject in need thereof comprising administering to thesubject a compound of Formula IV:

or a pharmaceutically acceptable salt thereof, wherein:

R₁ is C₁-C₆ alkyl, C₂-C₆ alkenyl, aryl, cycloalkyl, heterocyclyl,benzyl, hydroxyalkyl, or alkoxyalkyl;

R_(1a) is H or methyl;

R₂ is H, hydroxyl, or methoxy; and

R₃ and R₄ are each methyl, or alternatively, R₃ and R₄, together withthe carbon atoms to which they are attached, form a 6-memberedunsubstituted carbocyclic ring.

In one embodiment, the compound of Formula IV is:

In yet another aspect, provided herein is a method of treating adepressive symptom in a subject in need thereof comprising administeringto the subject a compound selected from Table A, or a pharmaceuticallyacceptable salt thereof.

TABLE A

In another aspect, provided herein is a method of treating depression ina subject in need thereof, comprising administering to the subject thecompound of Formulas (I), (II), (III), or (IV), or Table A, or apharmaceutically acceptable salt thereof.

In one embodiment, provided herein is a method of treating depression ina subject in need thereof, comprising administering to the subject thecompound of Formula (I) or a pharmaceutically acceptable salt thereof.

In another embodiment, provided herein is a method of treatingdepression in a subject in need thereof, comprising administering to thesubject the compound of Formula (II) or a pharmaceutically acceptablesalt thereof.

In still another embodiment, provided herein is a method of treatingdepression in a subject in need thereof, comprising administering to thesubject the compound of Formula (III) or a pharmaceutically acceptablesalt thereof.

In yet another embodiment, provided herein is a method of treatingdepression in a subject in need thereof, comprising administering to thesubject the compound of Formula (IV) or a pharmaceutically acceptablesalt thereof.

In yet another embodiment, provided herein is a method of treatingdepression in a subject in need thereof, comprising administering to thesubject the compound of Table A or a pharmaceutically acceptable saltthereof.

In yet another aspect, provided herein is a method of treating adepressive symptom in a subject in need thereof comprising administeringto the subject a compound selected from Table B, or a pharmaceuticallyacceptable salt thereof.

In yet another embodiment, provided herein is a method of treatingdepression in a subject in need thereof, comprising administering to thesubject the compound of Table B or a pharmaceutically acceptable saltthereof.

In one specific embodiment, provided herein is a method of treatingdepression and/or a depressive symptom in a subject in need thereof,comprising administering to the subject the compound:

or a pharmaceutically acceptable salt thereof.

In another embodiment, provided herein is a method of treatingdepression and/or a depressive symptom in a subject in need thereof,comprising administering to the subject the compound:

or a pharmaceutically acceptable salt thereof.

In still another embodiment, provided herein is a method of treatingdepression and/or a depressive symptom in a subject in need thereof,comprising administering to the subject the compound:

or a pharmaceutically acceptable salt thereof.

In still another embodiment, provided herein is a method of treatingdepression and/or a depressive symptom in a subject in need thereof,comprising administering to the subject the compound:

or a pharmaceutically acceptable salt thereof.

In one embodiment, the compound of Formulas (I), (II), (III), or (IV),or Table is a μ opioid receptor agonist having an Emax of 5% to 45%(e.g., 5, 10, 15, 20, 25, 30, 35, 40, or 45%) in a GTPγS binding assay.In one particular embodiment, the agonist exhibits an Emax of 15% to 35%in the GTPγS binding assay. In another embodiment, said agonist has alow risk of opioid dependence, opioid addiction and or symptoms ofopioid withdrawal.

In one embodiment, the compound of Formulas (I), (II), (III), or (IV),or Table A, is a compound that exhibits a maximal dopamine efflux in thenucleus accumbens in a rat of 125% to 300% (e.g., 125, 150, 175, 200,225, 250, 275, or 300%) over base line. In one particular embodiment,the maximal dopamine efflux in the nucleus accumbens of a rat is 200% to300% over base line. In another embodiment, the compound has a low riskof opioid dependence, opioid addiction and or symptoms of opioidwithdrawal.

In another embodiment, the compound of Formulas (I), (II), (III), or(IV), or Table A, is a compound that does not attenuate thermal pain ina rodent hot plate model when administered at of dose of at least 1mg/kg (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 mg/kg). In one embodiment,the compound does not attenuate thermal pain in a rodent hot plate modelwhen administered at a dose of 1-10 mg/kg (e.g., 1, 2, 3, 4, 5, 6, 7, 8,9, or 10 mg/kg). In one particular embodiment, the compound does notattenuate thermal pain in a rodent hot plate model when administered ata dose of at least 3 mg/kg. In another embodiment, the compound does notattenuate thermal pain in a rodent hot plate model when administered ata dose of 10 mg/kg. In another embodiment, the compound has a low riskof opioid dependence, opioid addiction and or symptoms of opioidwithdrawal.

In one particular embodiment of the above-described methods, the subjectis a human.

In another embodiment, the depressive symptom is depressed mood, loss ofpleasure, loss of appetite, sleep disturbance, psychomotor changes,fatigue, and/or post-partum depression.

In still another embodiment, the depressive symptom can be associatedwith a mental condition, wherein the mental condition is schizoaffectivedisorder, and/or seasonal affective disorder.

In yet another embodiment, the depressive symptom is acute stressdisorder, adjustment disorders with depressed mood, Asperger syndrome,attention deficit, bereavement, bipolar I disorder, bipolar II disorder,borderline and personality disorder, cyclothymia and dysthymia,depression such as major depressive disorder (MDD) andtreatment-resistant disorder (TRD), Dysthymic disorder, hyperactivitydisorder, impulse control disorder, mixed mania, obsessive-compulsivepersonality disorder (OCD), paranoid, post-traumatic stress disorder,seasonal affective disorder, self-injury separation, sleep disorder,substance-induced mood disorder, Tourette syndrome and tic disorder,and/or Trichotillomania.

In another embodiment, the depressive symptom is an anxiety disorder,wherein the anxiety disorder is generalized anxiety disorder, panic,agoraphobia, acute stress, and/or post-traumatic stress disorder.

In another embodiment, the depressive symptom is associated with chronicor recurrent depression.

DEFINITIONS

The term “treat,” “treated,” “treating” or “treatment” includes thediminishment or alleviation of at least one symptom associated or causedby the state, disorder or disease being treated. In certain embodiments,the treatment comprises bringing into contact with the opioid receptoran effective amount of a μ opioid receptor agonist, such as a compoundof Formulas (I), (II), (III), or (IV), or Table A.

The term “subject” is intended to be a mammal. Examples of subjectsinclude humans, dogs, cows, horses, pigs, sheep, goats, cats, mice,rabbits, rats, and transgenic non-human animals. In preferredembodiments, the subject is a human, e.g., a human suffering from adepressive symptom, pain, pruritis, diarrhea, irritable bowel syndrome,gastrointestinal motility disorder, obesity, respiratory depression,convulsions, coughing, hyperalgesia, or drug addiction.

As used to herein, the term “GTPγS binding assay” refers to the GTPγSbinding assay described in Example B1, herein. This GTPγS binding assayis performed under conditions such that the observed Emax value forbuprenorphine (CAS#52485-79-7) in this assay is at least 50% compared tobaseline.

As used to herein, the term “Emax” refers to the maximal observed effectof a compound. In certain embodiments, the Emax is the maximalpercentage increase of [35S]GTPγS binding induced by an agonist relativeto basal [35S]GTPγS binding in the absence of any drug.

As used to herein, the term “EC50” refers to the concentration of acompound required to achieve an effect that is 50% of the Emax.

As used to herein, the term “rodent hot plate model” refers to thethermal pain assay described in Example B2, herein.

As used herein the term “low risk of opioid dependence, opioid addictionand or symptoms of opioid withdrawal” refers to low “abuse liability.”Drugs with “abuse liability” are those associated with physical and/orpsychological dependence in humans, or with a probability for diversionfrom the intended medical condition for recreational use. There are avariety of animal models that can be used to assess the abuse liabilityof drugs. In general, these models use comparator drugs with known highabuse potential. For the opioid class of compounds, the most commoncomparator drug is morphine. Morphine has been shown clinically to havea high potential for abuse. Morphine produces a “drug high,” dependencywhen the drug is repeatedly administered, and withdrawal when the druguse is abruptly stopped. Each of these traits can be evaluated in animalmodels for a given experimental drug to determine its relative riskcompared to morphine. For example, efflux of nucleus accumbens dopaminecan be evaluated as a predictor of the high or euphoria followingadministration of the drug. A reduction in the maximal possible observedincrease in dopamine efflux would be correlated with a significantlylower degree of euphoria and a reduction in the abuse liabilityassociated with drug-liking. Similarly, the potential for dependence andwithdrawal can be determined in standard animal models in which the drugis administer 1-3 times per day, or by continual infusion for 5 to 14days, followed by abrupt withdrawal. For addictive opioids, abruptcessation of administration of the drug will cause withdrawalcharacterized by such traits as weight-loss associated with excessiveurination and defecation, increased shaking behavior, increased“jumping” activity, and reduced body temperature. These are quantitativemeasures that can be used to evaluate the relative risk for dependencycompared to morphine. The ability of a drug to induce withdrawal inopioid-dependent patients will also lead to a reduced abuse liabilityassociated with diversion of the drug. This feature can also be directlyassessed in animals by making them dependent on morphine, or anotheropioid agonist, and then precipitating withdrawal by the administrationof the drug. In certain embodiments, the compounds disclosed herein havea lower abuse liability (e.g., a lower risk of opioid dependence, opioidaddiction and or symptoms of opioid withdrawal) than buprenorphine.

As used herein, the term “alkyl” refers to a fully saturated branched orunbranched hydrocarbon moiety. Preferably the alkyl comprises 1 to 20carbon atoms, more preferably 1 to 16 carbon atoms, 1 to 10 carbonatoms, 1 to 7 carbon atoms, 1 to 6 carbons, 1 to 4 carbons, or 1 to 3carbon atoms. Representative examples of alkyl include, but are notlimited to, methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl,iso-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl,3-methylhexyl, 2,2-dimethylpentyl, 2,3-dimethylpentyl, n-heptyl,n-octyl, n-nonyl, n-decyl and the like. Furthermore, the expression“C_(x)-C_(y)-alkyl”, wherein x is 1-5 and y is 2-10 indicates aparticular alkyl group (straight- or branched-chain) of a particularrange of carbons. For example, the expression C₁-C₄-alkyl includes, butis not limited to, methyl, ethyl, propyl, butyl, isopropyl, tert-butyland isobutyl.

The term “alkenyl,” alone or in combination refers to a straight-chain,cyclic or branched hydrocarbon residue comprising at least one olefinicbond and the indicated number of carbon atoms. Preferred alkenyl groupshave up to 8, preferably up to 6, particularly preferred up to 4 carbonatoms. Examples of alkenyl groups are ethenyl, 1-propenyl, 2-propenyl,isopropenyl, 1-butenyl, 2-butenyl, 3-butenyl, isobutenyl,1-cyclohexenyl, 1-cyclopentenyl.

As used herein, the term “cycloalkyl” or “carbocyclic” refers tosaturated or unsaturated monocyclic, bicyclic or tricyclic hydrocarbongroups of 3-12 carbon atoms, preferably 3-9, or 3-7 carbon atoms.Exemplary monocyclic hydrocarbon groups include, but are not limited to,cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl andcyclohexenyl and the like. Exemplary bicyclic hydrocarbon groups includebornyl, indyl, hexahydroindyl, tetrahydronaphthyl, decahydronaphthyl,bicyclo[2.1.1]hexyl, bicyclo[2.2.1]heptyl, bicyclo[2.2.1]heptenyl,6,6-dimethylbicyclo[3.1.1]heptyl, 2,6,6-trimethylbicyclo[3.1.1]heptyl,bicyclo[2.2.2]octyl and the like. Exemplary tricyclic hydrocarbon groupsinclude adamantyl and the like.

“Alkoxyalkyl” refers to a group having the formula —R^(i)—OR^(ii),wherein R^(i) is an alkyl group as defined above, and OR^(ii) is analkoxy group as defined below.

“Alkoxy” refers to those alkyl groups, having from 1 to 10 carbon atoms,attached to the remainder of the molecule via an oxygen atom. Alkoxygroups with 1-8 carbon atoms are preferred. The alkyl portion of analkoxy may be linear, cyclic, or branched, or a combination thereof.Examples of alkoxy groups include methoxy, ethoxy, isopropoxy, butoxy,cyclopentyloxy, and the like. An alkoxy group can also be represented bythe following formula: —OR^(i), where R^(i) is the “alkyl portion” of analkoxy group.

The term “hydroxyalkyl” refers to a group having the formula—R^(iii)—OH, wherein R^(iii) is an alkyl group as defined above.

The term “aryl” includes aromatic monocyclic or multicyclic e.g.,tricyclic, bicyclic, hydrocarbon ring systems consisting only ofhydrogen and carbon and containing from six to nineteen carbon atoms, orsix to ten carbon atoms, where the ring systems may be partiallysaturated. Aryl groups include, but are not limited to, groups such asphenyl, tolyl, xylyl, anthryl, naphthyl and phenanthryl. Aryl groups canalso be fused or bridged with alicyclic or heterocyclic rings which arenot aromatic so as to form a polycycle (e.g., tetralin).

The term “heteroaryl,” as used herein, represents a stable monocyclic orbicyclic ring of up to 7 atoms in each ring, wherein at least one ringis aromatic and contains from 1 to 4 heteroatoms selected from the groupconsisting of O, N and S. Heteroaryl groups within the scope of thisdefinition include but are not limited to: acridinyl, carbazolyl,cinnolinyl, quinoxalinyl, pyrrazolyl, indolyl, benzotriazolyl, furanyl,thienyl, benzothienyl, benzofuranyl, quinolinyl, isoquinolinyl,oxazolyl, isoxazolyl, indolyl, pyrazinyl, pyridazinyl, pyridinyl,pyrimidinyl, pyrrolyl, tetrahydroquinoline. As with the definition ofheterocycle below, “heteroaryl” is also understood to include theN-oxide derivative of any nitrogen-containing heteroaryl. In cases wherethe heteroaryl substituent is bicyclic and one ring is non-aromatic orcontains no heteroatoms, it is understood that attachment is via thearomatic ring or via the heteroatom containing ring, respectively.

The term “heterocycle” or “heterocyclyl” refers to a five-member toten-member, fully saturated or partially unsaturated nonaromaticheterocylic groups containing at least one heteroatom such as O, S or N.The most frequent examples are piperidinyl, morpholinyl, piperazinyl,pyrrolidinyl or pirazinyl. Attachment of a heterocyclyl substituent canoccur via a carbon atom or via a heteroatom.

Moreover, the alkyl, alkenyl, cycloalkyl, cycloalkenyl, alkoxy, aryl,heteroaryl, and heterocycle groups described above can be“unsubstituted” or “substituted.” The term “substituted” is intended todescribe moieties having substituents replacing a hydrogen on one ormore atoms, e.g. C, O or N, of a molecule. Such substituents canindependently include, for example, one or more of the following:straight or branched alkyl (preferably C₁-C₅), cycloalkyl (preferablyC₃-C₈), alkoxy (preferably C₁-C₆), thioalkyl (preferably C₁-C₆), alkenyl(preferably C₂-C₆), alkynyl (preferably C₂-C₆), heterocyclic,carbocyclic, aryl (e.g., phenyl), aryloxy (e.g., phenoxy), aralkyl(e.g., benzyl), aryloxyalkyl (e.g., phenyloxyalkyl), arylacetamidoyl,alkylaryl, heteroaralkyl, alkylcarbonyl and arylcarbonyl or other suchacyl group, heteroarylcarbonyl, or heteroaryl group, (CR′R″)₀₋₃NR′R″(e.g., —NH₂), (CR′R″)₀₋₃CN (e.g., —CN), —NO₂, halogen (e.g., —F, —Cl,—Br, or —I), (CR′R″)₀₋₃C(halogen)₃ (e.g., —CF₃), (CR′R″)₀₋₃CH(halogen)₂,(CR′R″)₀₋₃CH₂(halogen), (CR′R″)₀₋₃CONR′R″, (CR′R″)₀₋₃(CNH)NR′R″,(CR′R″)₀₋₃S(O)₁₋₂NR′R″, (CR′R″)₀₋₃CHO, (CR′R″)₀₋₃O(CR′R″)₀₋₃H,(CR′R″)₀₋₃S(O)₀₋₃R′ (e.g., —SO₃H, —OSO₃H), (CR′R″)₀₋₃O(CR′R″)₀₋₃H (e.g.,—CH₂OCH₃ and —OCH₃), (CR′R″)₀₋₃S(CR′R″)₀₋₃H (e.g., —SH and —SCH₃),(CR′R″)₀₋₃OH (e.g., —OH), (CR′R″)₀₋₃COR′, (CR′R″)₀₋₃(substituted orunsubstituted phenyl), (CR′R″)₀₋₃(C₃-C₈ cycloalkyl), (CR′R″)₀₋₃CO₂R′(e.g., —CO₂H), or (CR′R″)₀₋₃OR′ group, or the side chain of anynaturally occurring amino acid; wherein R′ and R″ are each independentlyhydrogen, a C₁-C₅ alkyl, C₂-C₅ alkenyl, C₂-C₅ alkynyl, or aryl group.

As used herein, the term “acyl” refers to an organic radical linked to acarbonyl.

The present invention also includes pharmaceutically acceptable salts ofthe compounds described herein. As used herein, “pharmaceuticallyacceptable salts” refers to derivatives of the disclosed compoundswherein the parent compound is modified by converting an existing acidor base moiety to its salt form. Examples of pharmaceutically acceptablesalts include, but are not limited to, mineral or organic acid salts ofbasic residues such as amines; alkali or organic salts of acidicresidues such as carboxylic acids; and the like. The pharmaceuticallyacceptable salts of the present invention include the conventionalnon-toxic salts of the parent compound formed, for example, fromnon-toxic inorganic or organic acids. The pharmaceutically acceptablesalts of the present invention can be synthesized from the parentcompound which contains a basic or acidic moiety by conventionalchemical methods. Generally, such salts can be prepared by reacting thefree acid or base forms of these compounds with a stoichiometric amountof the appropriate base or acid in water or in an organic solvent, or ina mixture of the two; generally, nonaqueous media like ether, ethylacetate, ethanol, isopropanol, or acetonitrile are preferred. Lists ofsuitable salts are found in Remington's Pharmaceutical Sciences,17.sup.th ed., Mack Publishing Company, Easton, Pa., 1985, p. 1418 andJournal of Pharmaceutical Science, 66, 2 (1977), each of which isincorporated herein by reference in its entirety.

The description of the disclosure herein should be construed incongruity with the laws and principals of chemical bonding. For example,it may be necessary to remove a hydrogen atom in order accommodate asubstitutent at any given location. Furthermore, it is to be understoodthat definitions of the variables (i.e., “R groups”), as well as thebond locations of the generic formulae of the invention (e.g., FormulasI, II, III, or IV), will be consistent with the laws of chemical bondingknown in the art. It is also to be understood that all of the compoundsof the invention described above will further include bonds betweenadjacent atoms and/or hydrogens as required to satisfy the valence ofeach atom. That is, bonds and/or hydrogen atoms are added to provide thefollowing number of total bonds to each of the following types of atoms:carbon: four bonds; nitrogen: three bonds; oxygen: two bonds; andsulfur: two-six bonds.

The compounds of this invention may include asymmetric carbon atoms. Itis to be understood accordingly that the isomers arising from suchasymmetry (e.g., all enantiomers, stereoisomers, rotamers, tautomers,diastereomers, or racemates) are included within the scope of thisinvention. Such isomers can be obtained in substantially pure form byclassical separation techniques and by stereochemically controlledsynthesis. Furthermore, the structures and other compounds and moietiesdiscussed in this application also include all tautomers thereof.Compounds described herein may be obtained through art recognizedsynthesis strategies.

It will also be noted that the substituents of some of the compounds ofthis invention include isomeric cyclic structures. It is to beunderstood accordingly that constitutional isomers of particularsubstituents are included within the scope of this invention, unlessindicated otherwise. For example, the term “tetrazole” includestetrazole, 2H-tetrazole, 3H-tetrazole, 4H-tetrazole and 5H-tetrazole.

EXEMPLIFICATION OF THE INVENTION

The invention is further illustrated by the following examples, whichshould not be construed as further limiting. The practice of the presentinvention will employ, unless otherwise indicated, conventionaltechniques of cell biology, cell culture, molecular biology, transgenicbiology, microbiology and immunology, which are within the skill of theart.

Part A. Synthetic Procedures

Synthesis procedures for preparation of the compounds of the inventionare readily available to the ordinary skilled artisan. For example, U.S.Pat. No. 7,262,298; PCT publication WO2012/088494; U.S. Pat. No.8,252,929; U.S. Pat. No. 8,026,252; Neumeyer et al. (Journal of Med.Chem. 2012, p. 3878); and U.S. Pat. No. 8,252,929 provide synthesismethods that can be used or easily adapted to make the compounds ofFormulas I, II, III, and IV, and Table A. All of the above-referencedpatents and references are incorporated herein by reference in theirentirety.

The following are illustrative examples of synthesizing certainparticular compounds provided in this disclosure. One skilled in the artwill readily apply and/or adapt these methods to synthesize thecompounds provided herein, e.g., the compounds of Formulas I, II, III,and IV, and Table A.

General Procedure to Synthesize a NH Core Compound Synthesis of(4R,4aR,7aR,12bS)-3-methyl-1,2,3,4,4a,5,6,7a-octahydrospiro[4,12-methanobenzofuro[3,2-e]isoquinoline-7,2′-[1,3]dioxolan]-9-ol

To Hydromorphone HCl (15.0 g, 46.7 mmol) was added ethylene glycol (80mL) and methane sulfonic acid (10 mL) and the reaction heated at 80° C.overnight. The reaction was cooled to room temperature and poured intoice/NH_(3(aq)) (˜350 mL). The product was extracted with dichloromethaneand dried over MgSO₄ before concentration under reduced pressure to give(4R,4aR,7aR,12bS)-3-methyl-1,2,3,4,4a,5,6,7a-octahydrospiro[4,12-methanobenzofuro[3,2-e]isoquinoline-7,2′-[1,3]dioxolan]-9-ol(19 g, 99.9% LCMS); [M+H]⁺ 330.5. This was taken onto the next stepwithout purification.

Synthesis of(4R,4aR,7aR,12bS)-3-methyl-1,2,3,4,4a,5,6,7a-octahydrospiro[4,12-methanobenzofuro[3,2-e]isoquinoline-7,2′-[1,3]dioxolan]-9-yltrifluoromethanesulfonate

To a mixture of(4R,4aR,7aR,12bS)-3-methyl-1,2,3,4,4a,5,6,7a-octahydrospiro[4,12-methanobenzofuro[3,2-e]isoquinoline-7,2′-[1,3]dioxolan]-9-ol(21.54 g, 46.73 mmol) and triethylamine (20 mL, 140.2 mmol) indichloromethane (600 mL) was addedN-Phenylbis(trifluoromethanesulfonamide) (17.53 g, 49.0 mmol) and themixture stirred at room temperature overnight. The solvent wasconcentrated under reduced pressure and the residue taken up in 20%hexane in ethyl acetate (1 L) and washed with water (×5). The organicphase was dried (MgSO₄). Filtration and removal of the solvent underreduced pressure gave(4R,4aR,7aR,12bS)-3-methyl-1,2,3,4,4a,5,6,7a-octahydrospiro[4,12-methanobenzofuro[3,2-e]isoquinoline-7,2′-[1,3]dioxolan]-9-yltrifluoromethanesulfonate (20.77 g, 96% pure LCMS); [M+H]⁺ 462.1.

Synthesis of(4R,4aR,7aR,12bS)-3-methyl-1,2,3,4,4a,5,6,7a-octahydrospiro[4,12-methanobenzofuro[3,2-e]isoquinoline-7,2′-[1,3]dioxolane]-9-carbonitrile

To a solution of(4R,4aR,7aR,12bS)-3-methyl-1,2,3,4,4a,5,6,7a-octahydrospiro[4,12-methanobenzofuro[3,2-e]isoquinoline-7,2′-[1,3]dioxolan]-9-yltrifluoromethanesulfonate (20.77 g, 45.0 mmol) in degasseddimethylformamide (400 mL) was addedtetrakis(triphenylphosphine)palladium(0) (5.21 g, 4.50 mmol). Afterheating to 40° C., zinc cyanide (3.18 g, 27.0 mmol) was added and thereaction mixture heated at 110° C. for 6 hours. The reaction mixture wascooled to room temperature and diluted with ethyl acetate and filteredthrough a pad of celite. The filtrate was diluted further with ethylacetate and washed with water (3×500 mL). The aqueous phase was basifiedwith sodium hydrogen carbonate solution and re-extracted with ethylacetate and the combined organics dried (MgSO₄), filtered andconcentrated under reduced pressure. Purification by silicachromatography (100% dichloromethane to 5% NH₃/methanol indichloromethane) gave(4R,4aR,7aR,12bS)-3-methyl-1,2,3,4,4a,5,6,7a-octahydrospiro[4,12-methanobenzofuro[3,2-e]isoquinoline-7,2′-[1,3]dioxolane]-9-carbonitrile(10.0 g, 91% pure LCMS, 63% yield over three steps); [M+H]⁺ 339.1.

Synthesis of(4R,4aR,7aR,12bS)-1,2,3,4,4a,5,6,7a-octahydrospiro[4,12-methanobenzofuro[3,2-e]isoquinoline-7,2′-[1,3]dioxolane]-9-carbonitrile

To a suspension of(4R,4aR,7aR,12bS)-3-methyl-1,2,3,4,4a,5,6,7a-octahydrospiro[4,12-methanobenzofuro[3,2-e]isoquinoline-7,2′-[1,3]dioxolane]-9-carbonitrile(5.0 g, 17.8 mmol) in dimethylformamide (50 mL) was added diisopropylazodicarboxylate (5.4 mL, 27.5 mmol). The reaction was heated to 55° C.for 3 hours until the starting material was consumed. To the reactionwas added dimedone (5.8 g, 41.4 mmol) and methanol (1.75 mL, 54.8 mmol)and the reaction heated to 60° C. for 3 hours. The reaction was allowedto cool to room temperature and poured into 0.5 M HCl_((aq)) (50 mL).The aqueous phase was washed with diethyl ether: ethyl acetate (3:1).The organic phase was back extracted with 0.5 M HCl_((aq)) and acidicphases combined before basifying with 2M NaOH until pH9. The aqueousphase was extracted with ethyl acetate (×3). The combined organic phaseswere washed with water/brine (×3) before drying over MgSO₄ andconcentrating under reduced pressure. The residue was purified by silicachromatography (5% methanol in dichloromethane to 5% NH₃/methanol indichloromethane) to give(4R,4aR,7aR,12bS)-1,2,3,4,4a,5,6,7a-octahydrospiro[4,12-methanobenzofuro[3,2-e]isoquinoline-7,2′-[1,3]dioxolane]-9-carbonitrileas a pale yellow solid (3.90 g, 95% pure LCMS, 81% yield); [M+H]⁺ 325.1.

General Procedure to Synthesize a Deoxygenated Core Compound Synthesisof(4R,4aR,7aR,12bS)-9-(benzyloxy)-3-methyl-2,3,4,4a,5,6-hexahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinolin-7(7aH)-one

To Hydromorphone HCl (50.0 g, 155.3 mmol) in dimethylformamide (500 mL)was added sodium hydride (14.30 g, 357.4 mmol) portionwise with cooling.The addition was conducted over 25 minutes. The reaction was stirred atroom temperature for 1.5 hours before the addition of benzyl chloride(17.88 mL, 357.4 mmol) over 10 minutes with cooling. The reaction wasallowed to warm to room temperature and stirred for 40 hours. Thereaction was incomplete so additional benzyl chloride (1.79 mL, 15.5mmol) was added. After 4 hours, the reaction was quenched with water (60mL), acidified with aqueous HCl (2M, 800 mL) and washed with ethylacetate/diethyl ether (3:1) (2×800 mL). The aqueous phase was basifiedwith aqueous NaOH (2M, 800 mL) and extracted with ethyl acetate (2×1 L).The organic phases were combined, washed with water/brine (1:1) (2×800mL) and dried over MgSO₄ before concentration under reduced pressure.The residue was taken up in ethyl acetate and washed with water/brine(2×500 mL), dried over MgSO₄ before concentration under reduced pressureto give(4R,4aR,7aR,12bS)-9-(benzyloxy)-3-methyl-2,3,4,4a,5,6-hexahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinolin-7(7aH)-one(47.9 g, 95% pure by NMR, 82% yield); [M+H]⁺ 376.2. This was taken ontothe next step without purification.

Synthesis of(4bS,8aR,9R)-3-(benzyloxy)-4-hydroxy-11-methyl-8,8a,9,10-tetrahydro-5H-9,4b-(epiminoethano)phenanthren-6(7H)-one

To(4R,4aR,7aR,12bS)-9-(benzyloxy)-3-methyl-2,3,4,4a,5,6-hexahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinolin-7(7aH)-one(58.32 g, 0.16 mol) in ethanol (1.55 L) was added ammonium chloride(124.65 g, 2.33 mol) and zinc powder (101.59 g, 1.55 mol). The reactionwas heated to reflux and monitored by TLC. Once complete, the reactionwas allowed to cool and filtered through a pad of celite. The pad waswashed thoroughly with ethanol (1 L) and methanol (1 L). The filtratewas concentrated under reduced pressure. The residue was taken up indichloromethane and aqueous ammonia (˜15%, 1 L) before the product wasextracted with dichloromethane (3×700 mL). The dichloromethane phaseswere combined, washed with brine and dried over MgSO₄ before beingconcentrated under reduced pressure. The residue was purified by silicachromatography eluted with 10% methanol, 5% Et₃N in dichloromethane togive(4bS,8aR,9R)-3-(benzyloxy)-4-hydroxy-11-methyl-8,8a,9,10-tetrahydro-5H-9,4b-(epiminoethano)phenanthren-6(7H)-one(50.4 g, 74.3% pure LCMS, 64% yield); [M+H]⁺ 378.2.

Synthesis of(4bS,8aR,9R)-3-(benzyloxy)-11-methyl-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthren-4-yltrifluoromethanesulfonate

To a solution of(4bS,8aR,9R)-3-(benzyloxy)-4-hydroxy-1-methyl-8,8a,9,10-tetrahydro-5H-9,4b-(epiminoethano)phenanthren-6(7H)-one(28.2 g, 74.7 mmol) in tetrahydrofuran under an atmosphere of argon at0° C. was added sodium hydride (4.48 g, 112.1 mmol) portionwise. Thereaction was stirred for 30 minutes beforeN-Phenylbis(trifluoromethanesulfonamide) (40.03 g, 112.1 mmol) wasadded. The reaction was left to warm to room temperature overnight. Thereaction was cooled to 0° C. and quenched with IPA followed by water.The solution was diluted with ethyl acetate/heptanes (1:1) and aqueousammonia (30%, 400 mL) added. The phases were separated and the organicphase washed with aqueous ammonia (15%) twice before being washed withbrine, dried over MgSO₄ and concentrated under reduced pressure. Theresidue was purified by silica chromatography eluted with a gradientfrom 2.5-10% methanol/dichloromethane to give(4bS,8aR,9R)-3-(benzyloxy)-11-methyl-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthren-4-yltrifluoromethanesulfonate (31.6 g, 81% pure LCMS, 67% yield); [M+H]⁺510.2.

Synthesis of(4bS,8aR,9R)-3-(benzyloxy)-11-methyl-8,8a,9,10-tetrahydro-5H-9,4b-(epiminoethano)phenanthren-6(7H)-one

To a solution of(4bS,8aR,9R)-3-(benzyloxy)-11-methyl-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthren-4-yltrifluoromethanesulfonate (31.9 g, 62.6 mmol) in degasseddimethylformamide (320 mL) was added Pd(OAc)₂ (1.405 g, 6.6 mmol),1,3-bis(diphenylphosphino)propane (2.58 g, 6.3 mmol) and triethylsilane(100 mL, 626.0 mmol). The reaction was heated to 86° C. under argon for4 hours. The reaction was cooled to room temperature, quenched with 2MHCl and extracted with diethyl ether: ethyl acetate (1:1). The organicphase was washed with 2M HCl. The acid phases were combined and washedwith diethyl ether: ethyl acetate (1:1) (×3). The aqueous phase wasbasified with 2M NaOH and extracted with ethyl acetate (×3). The organicphase was washed with water (×3) and then brine before being dried overMgSO₄ and concentrated under reduced pressure to give(4bS,8aR,9R)-3-(benzyloxy)-11-methyl-8,8a,9,10-tetrahydro-5H-9,4b-(epiminoethano)phenanthren-6(7H)-one(20.2 g, 85% pure LCMS); [M+H]⁺ 362.3. This was taken onto the next stepwithout purification.

Synthesis of(4bS,8aR,9R)-3-(benzyloxy)-11-methyl-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]

To a suspension of(4bS,8aR,9R)-3-(benzyloxy)-11-methyl-8,8a,9,10-tetrahydro-5H-9,4b-(epiminoethano)phenanthren-6(7H)-one(20.2 g, 55.9 mmol) in ethylene glycol (280 mL) was added methanesulfonic acid (14.5 mL, 223.5 mmol). The reaction went into solution andwas stirred at room temperature for 16 hours. The reaction was pouredinto aqueous ammonia/ice and was extracted with ethyl acetate (×3). Theorganics were combined, washed with water/brine (×3) and dried overMgSO₄ and concentrated under reduced pressure to give(4bS,8aR,9R)-3-(benzyloxy)-11-methyl-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane](18.6g, 84% pure UPLC); [M+H]⁺ 406.3. This was taken onto the next stepwithout purification.

Synthesis of(4bS,8aR,9R)-11-methyl-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolan]-3-ol

To a solution of(4bS,8aR,9R)-3-(benzyloxy)-11-methyl-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane](21.8g, 53.8 mmol) in ethanol (545 mL) was added 10% palladium on carbon (2.2g, 0.1 eq by weight) and the reaction placed under an atmosphere ofhydrogen. The reaction was stirred for 16 hours at room temperature. Thereaction was filtered through a pad of celite and the filtrateconcentrated under reduced pressure to give(4bS,8aR,9R)-11-methyl-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolan]-3-ol(16.9 g, 73% pure LCMS); [M+H]⁺ 316.2. This was taken onto the next stepwithout purification.

Synthesis of(4bS,8aR,9R)-11-methyl-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolan]-3-yltrifluoromethanesulfonate

To a mixture of(4bS,8aR,9R)-11-methyl-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolan]-3-ol(16.95 g, 53.7 mmol) and triethylamine (22.5 mL, 161.2 mmol) indichloromethane (400 mL) was addedN-Phenylbis(trifluoromethanesulfonamide) (19.77 g, 55.4 mmol) and themixture stirred at room temperature overnight. The solvent wasconcentrated under reduced pressure and the residue taken up in ethylacetate. The organic phase was washed with aqueous ammonia/water (1:1×3)before washing with brine. The organic phase was dried over MgSO₄ andconcentrated under reduced pressure. The residue was purified by silicachromatography eluted with 0-10% methanol in dichloromethane to give(4bS,8aR,9R)-11-methyl-5,7,8,8a,9,10-hexahydrospirospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolan]-3-yltrifluoromethanesulfonate (18.7 g, 76.8% pure LCMS, 57.7% over 4 steps);[M+H]⁺ 448.2.

Synthesis of(4bS,8aR,9R)-11-methyl-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carbonitrile

To a solution of(4bS,8aR,9R)-11-methyl-5,7,8,8a,9,10-hexahydrospirospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolan]-3-yltrifluoromethanesulfonate (18.7 g, 41.8 mmol) in degasseddimethylformamide (250 mL) was addedtetrakis(triphenylphosphine)palladium(0) (4.83 g, 4.2 mmol). Afterheating to 40° C., zinc cyanide (2.94 g, 25.0 mmol) was added and thereaction mixture heated at 130° C. for 24 hours. Reaction incomplete socooled to room temperature and tetrakis(triphenylphosphine)palladium(0)(4.83 g, 4.2 mmol) was added and the reaction heated to 135° C. for 4hours. The reaction mixture was cooled to room temperature and dilutedwith ethyl acetate and quenched with sodium hydrogen carbonate solution.The mixture was filtered through a pad of celite. The phases wereseparated and the product extracted with ethyl acetate (×3). The organicphases were combined, washed with water/brine (×3), dried over MgSO₄ andconcentrated under reduced pressure. Purification by silicachromatography (100% dichloromethane to 5% NH₃/methanol indichloromethane) gave(4bS,8aR,9R)-11-methyl-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carbonitrile(8.26 g, 89% pure LCMS). [M+H]⁺ 325.2.

Synthesis of(4bS,8aR,9R)-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carbonitrile

To a suspension of(4bS,8aR,9R)-11-methyl-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carbonitrile(8.26 g, 25.5 mmol) in dimethylformamide (65 mL) was added diisopropylazodicarboxylate (9.32 mL, 47.4 mmol). The reaction was heated to 55° C.for 4 hours until starting material is consumed. To the reaction wasadded dimedone (9.99 g, 71.3 mmol) and methanol (3.1 mL, 94.2 mmol) andthe reaction heated to 60° C. for 3 hours. The reaction was allowed tocool to room temperature overnight. The reaction was poured into 0.5 MHCl_((aq)) (250 mL) and washed with diethyl ether: ethyl acetate (3:1).The organic phase was back extracted with 0.5 M HCl_((aq)) (250 mL) andthe acidic phases combined before basifying with 2M NaOH until pH9. Theaqueous phase was extracted with ethyl acetate (×3). The combinedorganic phases were washed with water/brine (×3) before drying overMgSO₄ and concentrating under reduced pressure. The residue was purifiedby silica chromatography (100% dichloromethane to 10% NH₃/methanol indichloromethane) to give(4bS,8aR,9R)-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carbonitrile(5.95 g, 42% yield over two steps, 92% pure LCMS); [M+H]⁺ 311.2.

A1. Experimental Procedure for Compound a and a Hydrochloride SaltThereof:

2-Cyclobutanecarbaldehyde

To a mixture of Pyridinium chlorochromate (41.3 g, 191.6 mmol) indichloromethane (120 mL) was added Cyclobutanemethanol (7.5 g, 87.1mmol). The mixture was stirred for 1.5 hours then filtered through a padof silica and rinsed with further dichloromethane (300 mL). The solventwas removed under reduced pressure to give 2-cyclobutylcarbaldehyde(10.0 g, contains residual dichloromethane) that was used withoutfurther purification.

(4R,4aS,7aR,12bS)-3-(cyclobutylmethyl)-4a,9-dihydroxy-2,3,4,4a,5,6-hexahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinolin-7(7aH)-one

A mixture of Noroxymorphone (8.8 g, 30.6 mmol) in methanol (250 mL) wasdegassed for 20 minutes. 2-cyclobutanecarbaldehyde (7.7 g, 91.5 mmol)was added and the mixture heated at reflux for 1 hour. The reactionmixture was cooled to ambient temperature. In a separate flask formicacid (14.0 g, 306 mmol) was added slowly to a solution of triethylamine(12.4 g, 123 mmol) in methanol (40 mL). The formic acid solution wasstirred for 5 minutes before being added to the solution containingNoroxymorphone along with dichloro(p-cymene)ruthenium(II) dimer (53 mg).The reaction was heated at reflux for a further 2.5 hours. The reactionwas concentrated under reduced pressure then partitioned between ethylacetate and saturated sodium bicarbonate solution. The aqueous phase wasextracted with further ethyl acetate then the organic layers combinedand dried (MgSO₄). Filtration and removal of the solvent under reducedpressure gave(4R,4aS,7aR,12bS)-3-(cyclobutylmethyl)-4a,9-dihydroxy-2,3,4,4a,5,6-hexahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinolin-7(7aH)-one(10.2 g, 94% yield); LC/MS (M+H)⁺=356.2.

(4R,4aS,7aR,12bS)-3-(cyclobutylmethyl)-4a-hydroxy-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinolin-9-yltrifluoromethanesulfonate

To a solution of(4R,4aS,7aR,12bS)-3-(cyclobutylmethyl)-4a,9-dihydroxy-2,3,4,4a,5,6-hexahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinolin-7(7aH)-one (10.2 g, 28.7 mmol) and triethylamine (12.2 mL, 88.3 mmol) indichloromethane (200 mL) was addedN-Phenylbis(trifluoromethanesulfonamide) (11.0 g, 30.9 mmol) and themixture stirred at room temperature overnight. The solvent wasconcentrated under reduced pressure and the residue partitioned between20% hexane in ethyl acetate (500 mL) and water (300 mL). The organiclayer was washed twice more with water and dried (MgSO₄). Filtration andremoval of the solvent under reduced pressure gave(4R,4aS,7aR,12bS)-3-(cyclobutylmethyl)-4a-hydroxy-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinolin-9-yltrifluoromethanesulfonate (14.3 g, 100% yield); LC/MS (M+H)⁺=488.1.

(4R,4aS,7aR,12bS)-3-(cyclobutylmethyl)-N-(2,4-dimethoxybenzyl)-4a-hydroxy-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinoline-9-carboxamide

To a solution of(4R,4aS,7aR,12bS)-3-(cyclobutylmethyl)-4a-hydroxy-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinolin-9-yltrifluoromethanesulfonate (14.3 g, 29.3 mmol) in degassed dimethylsulfoxide (185 mL), was added N-hydroxysuccinimide (6.8 g, 58.7 mmol),palladium acetate (0.66 g, 2.93 mmol), triethylamine (8.2 mL, 58.7 mmol)and 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (1.7 g, 2.93 mmol).The reaction mixture was heated with carbon monoxide (1 atm) at 75° C.overnight. The reaction mixture was cooled to ambient temperature and2,4-dimethoxybenzylamine (4.9 g, 29.3 mmol) added. The mixture wasstirred for 1 hour before partitioning between water (2 L) and ethylacetate (1 L). The aqueous phase was extracted twice more with ethylacetate. The combined organic phase was dried (MgSO₄), filtered, and thesolvent removed under reduced pressure. The crude material was purifiedby silica chromatography (3% methanol in dichloromethane) to give(4R,4aS,7aR,12bS)-3-(cyclobutylmethyl)-N-(2,4-dimethoxybenzyl)-4a-hydroxy-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinoline-9-carboxamide(14.4 g, 55% yield); LC/MS (M+H)⁺=533.3.

(4R,4aS,7aR,12bS)-3-(cyclobutylmethyl)-4a-hydroxy-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinoline-9-carboxamide

A mixture of(4R,4aS,7aR,12bS)-3-(cyclobutylmethyl)-N-(2,4-dimethoxybenzyl)-4a-hydroxy-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinoline-9-carboxamide(14.4 g, 27.0 mmol) in trifluoroacetic acid was stirred at ambienttemperature for 2 hours. The trifluoroacetic acid was removed underreduced pressure and the residue quenched with 300 mL of ammoniumhydroxide (6%). The product was extracted twice into dichloromethane(300 mL), the organic phases combined and dried (MgSO₄). Filtration andremoval of the solvent under reduced pressure gave(4R,4aS,7aR,12bS)-3-(cyclobutylmethyl)-4a-hydroxy-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinoline-9-carboxamide(9.0 g, 87% yield); LC/MS (M+H)⁺=383.2.

4bR,8aS,9R)-11-(cyclobutylmethyl)-4,8a-dihydroxy-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(Compound A

To a mixture of(4R,4aS,7aR,12bS)-3-(cyclobutylmethyl)-4a-hydroxy-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinoline-9-carboxamide(4.5 g, 11.8 mmol), and zinc powder (29.0 g, 444 mmol) in acetic acid(135 mL) was added conc. HCl (25.5 mL). The mixture was heated to 125°C. for 2 hours. The reaction mixture was cooled to ambient temperatureand quenched into ice/ammonium hydroxide solution (1 L, 28%). Theproduct was extracted into dichloromethane (1 L) and dried (MgSO₄).Filtration and removal of the solvent under reduced pressure gave thecrude material which was purified by silica chromatography (7.5%methanol/ammonia in DCM) followed by recrystallisation from methanol togive(4bR,8aS,9R)-11-(cyclobutylmethyl)-4,8a-dihydroxy-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(2.1 g, 46% yield); LC/MS (M+H)⁺=385.2.

(4bR,8aS,9R)-11-(cyclobutylmethyl)-4,8a-dihydroxy-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamidehydrochloride

To a solution of(4bR,8aS,9R)-11-(cyclobutylmethyl)-4,8a-dihydroxy-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(2.1 g, 5.46 mmol) in ethyl acetate (100 mL) was added 2N HCl/ether (6mL, 12 mmol) and the mixture stirred for 4 hours. The solvent wasremoved under reduced pressure and dried (55° C.) giving(4bR,8aS,9R)-11-(cyclobutylmethyl)-4,8a-dihydroxy-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamidehydrochloride (2.25 g, 98% yield); LC/MS (M+H)⁺=385.2. ¹H-NMR (400 MHz,DMSO) δ 8.98 (br s, 1H), 8.45 (s, 1H), 7.96 (s, 1H), 7.68 (d, 1H), 6.64(d, 1H), 6.33 (s, 1H), 3.85 (d, 1H), 3.45 (br s, 1H), 3.29 (br s,3H+H₂O), 3.15-2.91 (m, 2H), 2.74-2.60 (m, 3H), 2.40-2.10 (m, 2H),2.12-1.55 (m, 10H).

A2. Experimental Procedure for Compound D and a Hydrochloride SaltThereof:

4bR,6R,8aS,9R)-11-(cyclobutylmethyl)-4,6,8a-trihydroxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(Compound D

A solution of formamidinesulfinic acid (1.12 g, 10.4 mmol, 4.00 eq.) in0.5 M aqueous sodium hydroxide (20 mL) was added dropwise over 10minutes to a stirred solution of(4bR,8aS,9R)-11-(cyclobutylmethyl)-4,8a-dihydroxy-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide (1.00 g, 2.60 mmol, 1.00 eq.) in 0.5 NNaOH_((aq)) (30 mL) at ambient temperature under argon. The mixture washeated to 80° C. under argon for 12 hours and then cooled to roomtemperature. The precipitated solid was collected by filtration and thenwashed with water (2×10 mL) and diethyl ether (2×20 mL). The solid wasrecrystallised in methanol and then dried at 50° C. under vacuum for 3hours to leave(4bR,6R,8aS,9R)-11-(cyclobutylmethyl)-4,6,8a-trihydroxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamideas colourless crystals (400 mg, 40% yield); LC/MS (M+H)⁺=387.26.

(4bR,6R,8aS,9R)-11-(cyclobutylmethyl)-4,6,8a-trihydroxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamidehydrochloride

A solution of hydrochloric acid (0.40 mL, 2.0 M in diethyl ether) wasadded dropwise over 5 minutes to a stirred solution of(4bR,6R,8aS,9R)-11-(cyclobutylmethyl)-4,6,8a-trihydroxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide (400 mg, 1.03 mmol, 1.00 eq.) in ethylacetate (4 mL) at ambient temperature under argon. The mixture wasstirred at ambient temperature under argon for 3 hours and thenconcentrated under reduced pressure. The solid was dried at 50° C. undervacuum for 1 hour, and then freeze dried to leave(4bR,6R,8aS,9R)-11-(cyclobutylmethyl)-4,6,8a-trihydroxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamidehydrochloride as a colourless solid (379 mg, 87%); LC/MS (M+H)⁺=387.26.¹H NMR (300 MHz, CDCl3, 614-181-1_(—)1H-1.jdf): 14.43 (s, 1H), 8.80 (br.s, 1H), 8.47 (s, 1H), 7.95 (s, 1H), 7.69 (d, J=8.3 Hz, 1H), 6.63 (d,J=8.3 Hz, 1H), 5.69 (s, 1H), 4.45 (s, 1H), 3.31-3.08 (m, 6H), 3.00-2.81(m, 2H), 2.70-2.57 (m, 1H), 2.40-2.23 (m, 1H), 2.17-1.91 (m, 3H),1.90-1.70 (m, 4H), 1.67-1.31 (m, 6H).

A3. Experimental Procedure for Compound C and a Hydrochloride SaltThereof:

4bR,6S,8aS,9R)-11-(cyclobutylmethyl)-4,6,8a-trihydroxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(Compound C

A solution of K-selectride (7.80 mL, 7.80 mmol, 3.00 eq., 1.0 M intetrahydrofuran) was added dropwise over 15 minutes to a stirredsolution of(4bR,8aS,9R)-11-(cyclobutylmethyl)-4,8a-dihydroxy-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide (1.00 g, 2.60 mmol, 1.00 eq.) intetrahydrofuran (50 mL) at 0° C. under argon. The mixture was stirred at0° C. under argon for 2 hours and then water (20 mL) and methanol (50mL) were carefully added dropwise over 15 minutes. The mixture wasneutralised to pH 7 by addition of 2N HCl_((aq)). The mixture wasconcentrated under reduced pressure and the solid residue recrystallisedin methanol. The solid was washed with methanol (4 mL) and diethyl ether(2×10 mL), and then dried at 50° C. under vacuum for 3 hours to leave(4bR,6S,8aS,9R)-11-(cyclobutylmethyl)-4,6,8a-trihydroxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamideas colourless crystals (750 mg, 74%); LC/MS (M+H)⁺=387.3.

(4bR,6S,8aS,9R)-11-(cyclobutylmethyl)-4,6,8a-trihydroxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamidehydrochloride

A solution of hydrochloric acid (0.75 mL, 2.0 M in diethyl ether) wasadded dropwise over 5 minutes to a stirred solution of(4bR,6S,8aS,9R)-11-(cyclobutylmethyl)-4,6,8a-trihydroxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide (750 mg, 1.94 mmol) in ethyl acetate (10 mL)at ambient temperature under argon. The mixture was stirred at ambienttemperature under argon for 3 hours and then concentrated under reducedpressure. The solid was triturated with diethyl ether (2×10 mL), driedat 50° C. under vacuum for 1 hour, then freeze dried to leave(4bR,6S,8aS,9R)-11-(cyclobutylmethyl)-4,6,8a-trihydroxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamidehydrochloride as a colourless solid (695 mg, 85% yield); LC/MS(M+H)⁺=387.3. ¹H NMR (300 MHz, DMSO): δ 14.26 (s, 1H), 8.82 (br. s, 1H),8.36 (s, 1H), 7.79 (s, 1H), 7.60 (d, J=8.3 Hz, 1H), 6.56 (d, J=8.3 Hz,1H), 5.63 (s, 1H), 3.83 (s, 1H), 3.63 (s, 1H), 3.49-3.36 (m, 1H),3.29-3.08 (m, 4H), 2.97-2.80 (m, 2H), 2.72-2.58 (m, 1H), 2.36-2.20 (m,1H), 2.14-1.70 (m, 9H), 1.68-1.49 (m, 2H), 1.38-1.22 (m, 2H).

A4. Experimental Procedure for:

(2R,6R,11R)-tert-butyl8-hydroxy-6,11-dimethyl-1,2,5,6-tetrahydro-2,6-methanobenzo[d]azocine-3(4H)-carboxylate

A mixture of (-)-Normetazocine (5.0 g, 23.0 mmol), di-tert-butyldicarbonate (7.53 g, 34.5 mmol), and sodium hydrogen carbonate (5.80 g,69.0 mmol), in dichloromethane (170 mL), tetrahydrofuran (170 mL),methanol (85 mL) and water (500 mL) was stirred at ambient temperatureovernight. The organic phase was separated and the aqueous phase washedtwice with dichloromethane (500 mL). The combined organic phases weredried (MgSO₄). Filtration and removal of the solvent under reducedpressure gave oil that was dissolved in industrial methylated spirits(250 mL) and stirred with imidazole (3.0 g, 44.1 mmol) for 1 hour. Thesolvent was removed under reduced pressure and the residue partitionedbetween dichloromethane (250 mL) and 0.5N HCl_((aq)) (250 mL). Theorganic phase was washed with further acid (250 mL), brine (100 mL), anddried (MgSO₄). Filtration and removal of the solvent under reducedpressure gave (2R,6R,11R)-tert-butyl8-hydroxy-6,11-dimethyl-1,2,5,6-tetrahydro-2,6-methanobenzo[d]azocine-3(4H)-carboxylate(3.9 g, 53% yield); LC/MS(M+H)⁺=318.5.

(2R,6R,11R)-tert-butyl6,11-dimethyl-8-(((trifluoromethyl)sulfonyl)oxy)-1,2,5,6-tetrahydro-2,6-methanobenzo[d]azocine-3(4H)-carboxylate

To a solution of (2R,6R,11R)-tert-butyl8-hydroxy-6,11-dimethyl-1,2,5,6-tetrahydro-2,6-methanobenzo[d]azocine-3(4H)-carboxylate(3.9 g, 12.3 mmol) and triethylamine (5.1 mL, 36.9 mmol) indichloromethane (100 mL) was addedN-Phenylbis(trifluoromethanesulfonamide) (4.61 g, 12.9 mmol) and themixture stirred at ambient temperature for 4 hours. The solvent wasconcentrated under reduced pressure and the residue partitioned between20% hexane in ethyl acetate (500 mL) and water (400 mL). The organiclayer was washed four more times more with water and dried (MgSO₄).Filtration and removal of the solvent under reduced pressure gave(2R,6R,11R)-tert-butyl6,11-dimethyl-8-(((trifluoromethyl)sulfonyl)oxy)-1,2,5,6-tetrahydro-2,6-methanobenzo[d]azocine-3(4H)-carboxylate(5.32 g, 96% yield); LC/MS (M+H)⁺=450.4.

(2R,6R,11R)-tert-butyl8-((2,4-dimethoxybenzyl)carbamoyl)-6,11-dimethyl-1,2,5,6-tetrahydro-2,6-methanobenzo[d]azocine-3(4H)-carboxylate

To a solution of (2R,6R,11R)-tert-butyl6,11-dimethyl-8-(((trifluoromethyl)sulfonyl)oxy)-1,2,5,6-tetrahydro-2,6-methanobenzo[d]azocine-3(4H)-carboxylate(5.32 g, 11.8 mmol) in degassed dimethyl sulfone (50 mL), was addedN-hydroxysuccinimide (2.73 g, 23.7 mmol), palladium acetate (265 mg,1.18 mmol), triethylamine (3.3 mL, 23.7 mmol) and4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (683 mg, 1.18 mmol). Thereaction mixture was heated with carbon monoxide (1 atm) at 70° C.overnight. The reaction mixture was cooled to ambient temperature and2,4-dimethoxybenzylamine (2.17 mg, 13.0 mmol) added. The mixture wasstirred for 2 hours diluted with ethyl acetate (800 mL), and filteredthrough celite. The organic solution was washed twice with water (800mL), brine (300 mL), and dried (MgSO₄). Filtration and removal of thesolvent under reduced pressure gave crude material that was purified bysilica chromatography (EtOAc(1):heptanes(1)) to give(2R,6R,11R)-tert-butyl8-((2,4-dimethoxybenzyl)carbamoyl)-6,11-dimethyl-1,2,5,6-tetrahydro-2,6-methanobenzo[d]azocine-3(4H)-carboxylate(4.0 g, 68% yield); LC/MS(M+H)⁺=495.3.

(2R,6R,11R)—N-(2,4-dimethoxybenzyl)-6,11-dimethyl-1,2,3,4,5,6-hexahydro-2,6-methanobenzo[d]azocine-8-carboxamidehydrochloride

A mixture of (2R,6R,11R)-tert-butyl8-((2,4-dimethoxybenzyl)carbamoyl)-6,11-dimethyl-1,2,5,6-tetrahydro-2,6-methanobenzo[d]azocine-3(4H)-carboxylate(4.00 g, 8.09 mmol) in 4N HCl/dioxane was stirred at ambient temperatureovernight.

The majority of the solvent was decanted and the residue washed withdiethyl ether (500 mL). The resulting solid was dried under reducedpressure giving(2R,6R,11R)—N-(2,4-dimethoxybenzyl)-6,11-dimethyl-1,2,3,4,5,6-hexahydro-2,6-methanobenzo[d]azocine-8-carboxamidehydrochloride (3.35 g, 96% yield); LC/MS (M+H)⁺=395.5.

(2R,6R,11R)—N-(2,4-dimethoxybenzyl)-3-(2-methoxyethyl)-6,11-dimethyl-1,2,3,4,5,6-hexahydro-2,6-methanobenzo[d]azocine-8-carboxamide

A mixture of2R,6R,11R)—N-(2,4-dimethoxybenzyl)-6,11-dimethyl-1,2,3,4,5,6-hexahydro-2,6-methanobenzo[d]azocine-8-carboxamidehydrochloride (400 mg, 0.93 mmol), potassium carbonate (385 mg, 2.78mmol), and bromoethyl methyl ether (142 mg, 1.02 mmol) in acetonitrile(15 mL) was heated at 65° C. overnight. Further bromoethyl methyl etherwas added (70 mg, 0.50 mmol) and the reaction heated at 65° C. for 24hours. The reaction mixture was allowed to return to ambient temperaturebefore partitioning between ethyl acetate (100 mL) and water (100 mL).The organic phase was dried (MgSO₄). Filtration and removal of thesolvent under reduced pressure gave(2R,6R,11R)—N-(2,4-dimethoxybenzyl)-3-(2-methoxyethyl)-6,11-dimethyl-1,2,3,4,5,6-hexahydro-2,6-methanobenzo[d]azocine-8-carboxamide(360 mg, 86% yield); LC/MS (M+H)⁺=453.2.

(2R,6R,11R)-3-(2-methoxyethyl)-6,11-dimethyl-1,2,3,4,5,6-hexahydro-2,6-methanobenzo[d]azocine-8-carboxamide

A mixture of(2R,6R,11R)—N-(2,4-dimethoxybenzyl)-3-(2-methoxyethyl)-6,11-dimethyl-1,2,3,4,5,6-hexahydro-2,6-methanobenzo[d]azocine-8-carboxamide(360 mg, 0.80 mmol) in trifluoroacetic acid (5 mL) was stirred atambient temperature for 2 hours. The mixture was concentrated underreduced pressure before quenching with ice/ammonium hydroxide (28%) (25mL). The crude product was extracted twice using dichloromethane (100mL) and the combined organic layers dried (MgSO₄). Filtration andremoval of the solvent under reduced pressure gave the crude productthat was purified by prep-HPLC giving(2R,6R,11R)-3-(2-methoxyethyl)-6,11-dimethyl-1,2,3,4,5,6-hexahydro-2,6-methanobenzo[d]azocine-8-carboxamide(130 mg, 54% yield); LC/MS (M+H)⁺=303.2.

2R,6R,11R)-3-(2-methoxyethyl)-6,11-dimethyl-1,2,3,4,5,6-hexahydro-2,6-methanobenzo[d]azocine-8-carboxamidehydrochloride (Compound 14

To a solution of(2R,6R,11R)-3-(2-methoxyethyl)-6,11-dimethyl-1,2,3,4,5,6-hexahydro-2,6-methanobenzo[d]azocine-8-carboxamide(130 mg, 0.43 mmol) in ethyl acetate (10 mL) was added 2N HCl/ether (320μL, 0.64 mmol) and the mixture stirred for 1.5 hours. The solvent wasremoved under reduced pressure then freeze dried giving(2R,6R,11R)-3-(2-methoxyethyl)-6,11-dimethyl-1,2,3,4,5,6-hexahydro-2,6-methanobenzo[d]azocine-8-carboxamidehydrochloride (131 mg, 90% yield); LC/MS (M+H)⁺=303.22. ¹H-NMR (300 MHz,DMSO) δ 10.59-10.44 (br d, 1H), 7.96 (s, 1H), 7.78 (s, 1H), 7.68 (d,1H), 7.31 (d, 1H), 7.20 (d, 1H), 3.84-3.49 (m, 3H), 3.49-2.95 (6H+H₂O),2.43-2.20 (m, 2H), 2.16-1.97 (m, 2H), 1.54-1.23 (m, 2H), 0.87-0.66 (m,3H).

A5. Experimental Procedure for:

(4bS,9R)-4-hydroxy-3-methoxy-11-methyl-8,8a,9,10-tetrahydro-5H-9,4b-(epiminoethano)phenanthren-6(7H)-one(A) and(4bR,9R)-3-methoxy-11-methyl-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthren-4-ol(B)

To a mixture of hydrocodone (2×22 g (2 batches), 147 mmol) and zincpowder (2×115 g, 3.46 mol) in acetic acid (2×1 L) was added conc. HCl(2×50 mL). The reaction was heated at 125° C. for 3 hours. Bothreactions were combined and filtered. The zinc wash washed withindustrial methylated spirits (1 L), and dichloromethane (1 L). Bothorganic washes and the acetic acid solution were concentrated underreduced pressure and the residue basified with ice/ammonium hydroxide(28%). The crude product was extracted into dichloromethane and dried(MgSO₄). Filtration and removal of the solvent under reduced pressuregave the crude products that were purified by silica chromatography (3%methanol/ammonia in dichloromethane) giving three batches of varyingpurity (2.4 g, (B); 20.5 g, 50% (A), 50% (B); 12.5 g, 65% (A), 10% (B));LC/MS (M+H)⁺=302.1 (A); LC/MS (M+H)⁺=288.2 (B).

(4bS,9R)-3-methoxy-11-methyl-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthren-4-yltrifluoromethanesulfonate (C) and(4bR,9R)-3-methoxy-11-methyl-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthren-4-yltrifluoromethanesulfonate (D)

To a solution containing a (1:1) mixture of(4bS,9R)-4-hydroxy-3-methoxy-11-methyl-8,8a,9,10-tetrahydro-5H-9,4b-(epiminoethano)phenanthren-6(7H)-one(A) and(4bR,9R)-3-methoxy-11-methyl-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthren-4-ol(B) (20.5 g, 69.4 mmol) in tetrahydrofuran at 0° C. under an argonatmosphere was added sodium hydride (4.18 g, 60% in mineral oil, 104.5mmol). After 30 minutes N-Phenylbis(trifluoromethanesulfonamide) (37.3g, 104.4 mmol) was added and the mixture allowed to slowly return toambient temperature. The reaction was quenched with saturated aqueoussodium bicarbonate solution (500 mL) and extracted into ethyl acetate (1L). The organic phase was washed with brine and dried (MgSO₄).Filtration and removal of the solvent under reduced pressure gave thecrude product that was purified by silica chromatography (2.5%methanol/ammonia in dichloromethane) giving two batches of varyingpurity (11.0 g, (D); 15.1 g, 62% (C), 33% (D); LC/MS (M+H)⁺=434.1 (C);LC/MS (M+H)⁺=420.1 (D).

(4bR,9R)-3-methoxy-11-methyl-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene

A mixture of(4bR,9R)-3-methoxy-11-methyl-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthren-4-yltrifluoromethanesulfonate (D) (11.0 g, 26.2 mmol), palladium acetate(590 mg, 2.63 mmol), 1,3-bis(diphenylphosphino)propane (1.08 g, 2.61mmol) and triethylsilane (10.0 mL, 62.6 mmol) in dimethylformamide(degassed) was heated at 60° C. overnight under an argon atmosphere. Thereaction mixture was cooled to ambient temperature and partitionedbetween ethyl acetate (1 L) and water (1 L). The organic phase waswashed twice more with water (2×500 mL). The combined aqueous phaseswere extracted using dichloromethane (2 L total). The organic phasecontaining dichloromethane and dimethyl formamide was concentrated underreduced pressure and the crude product purified by silica chromatography(3% methanol/ammonia in dichloromethane).

The same procedure was carried out with the 15.1 g batch (62% (C), 33%(D)). The material was purified as described above to give(4bR,9R)-3-methoxy-11-methyl-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene(8.6 g); LC/MS (M+H)⁺=272.0.

(4bR,9R)-3-methoxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene

To a solution of(4bR,9R)-3-methoxy-11-methyl-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene(5.0 g, 18.44 mmol) in dichloromethane (400 mL) was added a solution ofCNBr (17 mL, 51 mmol, 3N in dichloromethane) under an argon atmosphere.The mixture was heated at reflux overnight. The solvent was removedunder reduced pressure and to the residue was added diethyleneglycol(100 mL) and KOH (16.6 g, 296 mmol). The reaction mixture was heated at160° C. for 2 hours, allowed to return to ambient temperature, thenpartitioned between dichloromethane (600 mL) and water (1 L). Theaqueous phase was washed twice more with dichloromethane and thecombined organic fractions dried (MgSO₄). Filtration and removal of thesolvent under reduced pressure gave the crude product that was purifiedby silica chromatography (10% methanol/ammonia in DCM) giving(4bR,9R)-3-methoxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene(4.02 g, 85% yield); LC/MS (M+H)⁺=258.5.

(4bR,9R)-11-(1-cyclopropylethyl)-3-methoxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene

A mixture of(4bR,9R)-3-methoxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene(1.41 g), methylcyclopropyl ketone (17 mL, 172 mmol), and acetic acidwere heated at 70° C. for 1 hour. Sodium cyanoborohydride was added (830mg, 13.2 mmol) and the mixture heated at 70° C. overnight. The reactionmixture was portioned between ethyl acetate (500 mL) and saturatedsodium bicarbonate (500 mL). The organic phase was washed with brine anddried (MgSO₄). Filtration and removal of the solvent under reducedpressure gave the crude product that was purified by silicachromatography (2% methanol/ammonia in dichloromethane) giving(4bR,9R)-11-(1-cyclopropylethyl)-3-methoxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene(0.75 g, 42% yield); LC/MS (M+H)⁺=326.1.

(4bR,9R)-11-(1-cyclopropylethyl)-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthren-3-ol

To an ice cooled solution of(4bR,9R)-11-(1-cyclopropylethyl)-3-methoxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene(0.75 g, 2.31 mmol) in dichloromethane (50 mL) was added BBr₃ (0.9 mL,9.23 mmol) dropwise under an argon atmosphere. The reaction was stirredfor 3 hours then quenched with ammonia/methanol. The solvent was removedunder reduced pressure giving(4bR,9R)-11-(1-cyclopropylethyl)-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthren-3-ol(0.75 g, 100% yield); LC/MS (M+H)⁺=312.1.

(4bR,9R)-11-(1-cyclopropylethyl)-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthren-3-yltrifluoromethanesulfonate

To a solution of(4bR,9R)-11-(1-cyclopropylethyl)-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthren-3-ol(0.75 g, 2.41 mmol) and triethylamine (1.0 mL, 7.23 mmol) indichloromethane (50 mL) was addedN-Phenylbis(trifluoromethanesulfonamide) (0.95 g, 2.65 mmol) and themixture stirred at room temperature overnight. The solvent wasconcentrated under reduced pressure and the residue partitioned between20% hexane in ethyl acetate (300 mL) and water (150 mL). The organiclayer was washed four more times more with water and dried (MgSO₄).Filtration and removal of the solvent under reduced pressure gave(4bR,9R)-11-(1-cyclopropylethyl)-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthren-3-yltrifluoromethanesulfonate (0.78 g, 73% yield); LC/MS (M+H)⁺=444.1.

(4bR,9R)-11-(1-cyclopropylethyl)-N-(2,4-dimethoxybenzyl)-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide

To a solution of(4bR,9R)-11-(1-cyclopropylethyl)-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthren-3-yltrifluoromethanesulfonate (0.78 g, 1.76 mmol) in degassed dimethylsulfoxide (15 mL), was added N-hydroxysuccinimide (405 mg, 3.52 mmol),palladium acetate (79 mg, 0.352 mmol), triethylamine (490 μL, 3.52 mmol)and 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (203 mg, 0.352mmol). The reaction mixture was heated with carbon monoxide (1 atm) at75° C. overnight. The reaction mixture was cooled to ambient temperatureand 2,4-dimethoxybenzylamine (294 mg, 1.76 mmol) added. The mixture wasstirred for 1 hour before partitioning between water (300 mL) and ethylacetate (400 mL). The aqueous phase was extracted twice more with ethylacetate. The combined organic phase was dried (MgSO₄), filtered, and thesolvent removed under reduced pressure. The crude material was purifiedby silica chromatography (3% methanol in dichloromethane) to give(4bR,9R)-11-(1-cyclopropylethyl)-N-(2,4-dimethoxybenzyl)-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(1.0 g, contains impurities—used directly in next step); LC/MS(M+H)⁺=489.1.

(4bR,9R)-11-((R)-1-cyclopropylethyl)-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide

A mixture of(4bR,9R)-11-(1-cyclopropylethyl)-N-(2,4-dimethoxybenzyl)-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(1.0 g, 2.05 mmol) in trifluoroacetic acid (30 mL) was stirred at roomtemperature for 2 hours. The mixture was concentrated under reducedpressure before quenching with ice/ammonium hydroxide (28%) (50 mL). Thecrude product was extracted twice using dichloromethane (200 mL) and thecombined organic layers dried (MgSO₄). Filtration and removal of thesolvent under reduced pressure gave the crude product that was purifiedand separated from the (S)-diastereomer using prep-HPLC giving(4bR,9R)-11-((R)-1-cyclopropylethyl)-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(64 mg, 10% yield); LC/MS (M+H)⁺=339.3.

(4bR,9R)-11-((R)-1-cyclopropylethyl)-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamidehydrochloride

To a solution of(4bR,9R)-11-((R)-1-cyclopropylethyl)-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(64 mg, 0.19 mmol) in ethyl acetate (15 mL) was added 2N HCl/ether (140μL, 0.28 mmol) and the mixture stirred for 30 minutes. The solvent wasremoved under reduced pressure then freeze dried giving(4bR,9R)-11-((R)-1-cyclopropylethyl)-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamidehydrochloride (71 mg, 100% yield); LC/MS (M+H)⁺=339.3. ¹H-NMR (400 MHz,DMSO) δ 10.41 (br s, 1H), 7.95 (s, 1H), 7.81 (s, 1H), 7.68 (d, 1H), 7.30(s, 1H), 7.22 (d, 1H), 4.18 (s, 1H), 3.57-3.03 (m, 3H+H₂O), 2.95 (d,1H), 2.55 (d, 1H), 2.37-2.16 (m, 2H), 2.08-1.87 (m, 1H), 2.68-0.51 (m,15H), 0.20 (s, 1H).

A6. Experimental Procedure for Compound E and a Hydrochloride SaltThereof Synthesis of(4R,4aR,7aR,12bS)-3-(cyclobutylmethyl)-1,2,3,4,4a,5,6,7a-octahydrospiro[4,12-methanobenzofuro[3,2-e]isoquinoline-7,2′-[1,3]dioxolane]-9-carbonitrile

To a solution of cyclobutane carboxaldehyde (19.45 g, 231.2 mmol) indichloromethane (500 mL) was added(4R,4aR,7aR,12bS)-1,2,3,4,4a,5,6,7a-octahydrospiro[4,12-methanobenzofuro[3,2-e]isoquinoline-7,2′-[1,3]dioxolane]-9-carbonitrile(25 g, 77.1 mmol). The reaction was stirred for 60 minutes at roomtemperature before sodium triacetoxyborohydride (32.7 g, 154.0 mmol) wasadded portionwise over 20 minutes. After one hour, the reaction wasquenched with NaHCO₃ solution and extracted with dichloromethane (×3).The dichloromethane phases were combined, washed with brine, dried overMgSO₄ and concentrated under reduced pressure. The residue was purifiedby silica chromatography eluted with dichloromethane to 7% methanol indichloromethane to give(4R,4aR,7aR,12bS)-3-(cyclobutylmethyl)-1,2,3,4,4a,5,6,7a-octahydrospiro[4,12-methanobenzofuro[3,2-e]isoquinoline-7,2′-[1,3]dioxolane]-9-carbonitrile(31.1 g, 98% pure LCMS, assume quant.); [M+H]⁺ 393.1.

Synthesis of(4R,4aR,7aR,12bS)-3-(cyclobutylmethyl)-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinoline-9-carbonitrile

A suspension of(4R,4aR,7aR,12bS)-3-(cyclobutylmethyl)-1,2,3,4,4a,5,6,7a-octahydrospiro[4,12-methanobenzofuro[3,2-e]isoquinoline-7,2′-[1,3]dioxolane]-9-carbonitrile(31.1 g, 79.2 mmol) in 6M HCl (aq) (250 mL) was stirred at roomtemperature at room temperature for 24 hours. Further 6M HCl was added(25 mL) and stirred for an additional 24 hours. The reaction was pouredonto ice/NH_(3(aq)) and stirred for 30 minutes and the solid collectedby suction filtration and washed with water. The solid was dissolved indichloromethane and washed with brine, dried over MgSO₄ and concentratedunder reduced pressure to give(4R,4aR,7aR,12bS)-3-(cyclobutylmethyl)-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinoline-9-carbonitrile(26.1 g, 96% pure LCMS, 95% yield); [M+H]⁺ 367.2.

Synthesis of(4R,4aR,7aR,12bS)-3-(cyclobutylmethyl)-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinoline-9-carboxamide

To a solution of(4R,4aR,7aR,12bS)-3-(cyclobutylmethyl)-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinoline-9-carbonitrile(24 g, 68.9 mmol) in tert-butanol (240 mL) was added KOH (2.1 g, 37.1mmol). The reaction was heated to 100° C. for 15 minutes. The reactionwas allowed to cool to room temperature and concentrated to 50% volume.Diluted with water and extracted with ethyl acetate twice. The organicphases were combined, washed with sodium hydrogen carbonate solution andbrine and dried over MgSO₄ and concentrated under reduced pressure. Theresidue was purified by silica chromatography eluted with 4% methanol indichloromethane to give to give(4R,4aR,7aR,12bS)-3-(cyclobutylmethyl)-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinoline-9-carboxamide(14.2 g, 89% pure LCMS, 56% yield); [M+H]⁺ 367.2.

Synthesis of(4bS,8aR,9R)-11-(cyclobutylmethyl)-4-hydroxy-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(Compound E)

To a solution of(4R,4aR,7aR,12bS)-3-(cyclobutylmethyl)-7-oxo-2,3,4,4a,5,6,7,7a-octahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinoline-9-carboxamide(14.2 g, 38.75 mmol) in ethanol (500 mL) was added ammonium chloride(31.1 g, 581 mmol) followed by zinc powder (25.3 g, 388 mmol). Thereaction was heated to reflux for 2.5 hours. The reaction was cooled to˜50° C. and filtered through a pad of celite. The celite was washed withethanol/methanol. The filtrate was concentrated under reduced pressure.The residue was partitioned between dichloromethane and NH_(3(aq))/H₂O(1:1) and the aqueous phase re-extracted with dichloromethane. Thecombined dichloromethane phase was washed with brine, dried over MgSO₄and concentrated. The crude product was purified by silicachromatography and eluted with 3.5% NH₃/methanol in dichloromethane togive(4bS,8aR,9R)-11-(cyclobutylmethyl)-4-hydroxy-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(9.7 g, 98.5% pure LCMS, 68% yield); [M+H]⁺ 369.2.

Synthesis of(4bS,6S,8aR,9R)-11-(cyclobutylmethyl)-4,6-dihydroxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamidehydrochloride

1M K-selectride in tetrahydrofuran (49.9 mL) was added to a solution of(4bS,8aR,9R)-11-(cyclobutylmethyl)-4-hydroxy-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(9.2 g, 25.0 mmol) in tetrahydrofuran (150 mL) cooled in an ice bath.After 30 minutes a saturated solution of ammonium chloride was added andthe reaction mixture extracted with ethyl acetate (×3). The combinedorganic phase was washed with sodium hydrogen carbonate solution andbrine, dried over MgSO₄ and concentrated. The residue was taken up in 2MHCl aq and washed with ethyl acetate. The aqueous phase was basifiedwith 2 M NaOH to pH 7 then sodium hydrogen carbonate solution was added.The aqueous solution was extracted with dichloromethane (×3) dried overMgSO₄, concentrated, and purified via prep HPLC (30-50% acetonitrile in0.1% NH₄HCO₃ pH10 buffer) to give(4bS,8aR,9R)-11-(cyclobutylmethyl)-4-hydroxy-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(4.7 g, 99.76% pure LCMS, 51% yield); [M+H]⁺ 371.19.

To a solution of(4bS,8aR,9R)-11-(cyclobutylmethyl)-4-hydroxy-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(4.6 g, 12.4 mmol) in ethyl acetate (30 mL) and dichloromethane (30 mL)was added 2M HCl in diethyl ether (7.45 mL, 14.9 mmol). After 2 hours,the liquors were removed under reduced pressure and the residuesuspended in diethyl ether, collected by suction filtration and washedwith diethyl ether. The solid was dissolved in 9:1 water/methanol andfreeze dried to give(4bS,6S,8aR,9R)-11-(cyclobutylmethyl)-4,6-dihydroxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamidehydrochloride (4.7 g, 99.81% pure LCMS, 93% yield); [M+H]⁺ 371.19. ¹HNMR (300 MHz, D₂O) 7.37 (1H, d), 6.62 (1H, d), 3.99 (1H, br s), 3.66(1H, br d), 3.51 (1H, br s), 2.91-3.27 (5H, m), 2.44-2.62 (2H, m),1.23-2.05 (14H, m).

A7. Experimental Procedure for Compound B and a Hydrochloride SaltThereof Synthesis of(4bS,8aR,9R)-11-(cyclopropylmethyl)-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carbonitrile

To a solution of(4bS,8aR,9R)-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carbonitrile(3.58 g, 11.5 mmol) in dichloromethane (115 mL) was addedcyclopropylcarboxaldehyde (2.55 mL, 34.6 mmol). The reaction was stirredfor 60 minutes at room temperature before sodium triacetoxyborohydride(4.90 g, 23.1 mmol) was added portionwise. After one hour, the reactionwas quenched with aqueous NaHCO₃ solution and extracted withdichloromethane (×3). The dichloromethane phases were combined, washedwith brine, dried over MgSO₄ and concentrated under reduced pressure.The residue was purified by silica chromatography eluted withdichloromethane to 5% methanol in dichloromethane to give(4bS,8aR,9R)-11-(cyclopropylmethyl)-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carbonitrile(3.59 g, 98.5% pure LCMS, 86% yield); [M+H]⁺ 365.2.

Synthesis of(4bS,8aR,9R)-11-(cyclopropylmethyl)-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carboxamide

To a solution of(4bS,8aR,9R)-11-(cyclopropylmethyl)-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carbonitrile(3.95 g, 9.9 mmol) in dimethylsulfoxide (40 mL) was added potassiumcarbonate (4.09 g, 29.6 mmol). The reaction was cooled to 15° C. andhydrogen peroxide (12 mL, 35% aqueous solution) added dropwisemaintaining the temperature between 15 and 20° C. After addition wascomplete, the reaction was allowed to warm to room temperature. Thereaction was cooled to 0° C., quenched with water and extracted withethyl acetate. The reaction was basified with sodium hydrogen carbonatesolution to pH 10 and extracted with ethyl acetate (×3). The organicswere combined, washed with water (×3), brine, dried over MgSO₄ andconcentrated under reduced pressure. The product was purified by silicachromatography eluted with a gradient from 100% dichloromethane to 10%NH₃/methanol in dichloromethane to give(4bS,8aR,9R)-11-(cyclopropylmethyl)-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carboxamide(2.76 g, 98.3% pure LCMS, 73% yield); [M+H]⁺ 383.2.

Synthesis of(4bS,8aR,9R)-11-(cyclopropylmethyl)-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamidehydrochloride

To(4bS,8aR,9R)-11-(cyclopropylmethyl)-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carboxamide(2.76 g, 7.2 mmol) was added 6M HCl (aq) (60 mL) with cooling. After anhour the reaction was poured onto ice/NH_(3(aq)) and extracted withdichloromethane (×3). The dichloromethane phases were combined, washedwith brine, dried over MgSO₄ and concentrated under reduced pressure.The residue was purified by silica chromatography eluted with 100%dichloromethane to 10% NH₃/methanol in dichloromethane to give CompoundB:(4bS,8aR,9R)-11-(cyclopropylmethyl)-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(2.41 g, 97.5% pure LCMS, 96% yield).

To(4bS,8aR,9R)-11-(cyclopropylmethyl)-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(2.39 g, 7.1 mmol) in ethyl acetate (60 mL) was added 2M HCl in diethylether (3.87 mL, 7.8 mmol). The product precipitated from solution andwas collected by filtration. The solid was washed with ethyl acetate anddiethyl ether before drying under vacuum. The product was dissolved inwater and freeze dried to give(4bS,8aR,9R)-11-(cyclopropylmethyl)-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamidehydrochloride (2.62 g, 99.9% LCMS, 99% yield); [M+H]⁺ 339.3. ¹H NMR (300MHz, D₂O) 7.60 (1H, s), 7.43 (1H, d), 7.17 (1H, d), 4.07 (0.8H, d), 3.97(0.2H, d), 2.34-3.44 (10H, m), 1.74-2.18 (3H, m), 1.60 (0.8H, d), 1.44(0.2H, d), 1.27 (1H, dq), 0.96 (1H, m), 0.59 (2H, d), 0.25 (2H, m).

A8. Experimental Procedure for:

Synthesis of(4bS,8aR,9R)-11-(cyclobutylmethyl)-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carbonitrile

To a solution of cyclobutylmethanol (3.70 g, 42.9 mmol) indichloromethane (100 mL) was added silica (25 g), followed by pyridiniumchlorochromate (18.52 g, 85.9 mmol). The reaction mixture was stirredfor 2 h and filtered through a plug of silica eluting withdichloromethane (300 mL). The resulting solution was concentrated toabout 75 mL and(4bS,8aR,9R)-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carbonitrile(0.40 g, 0.13 mmol) added, followed by sodium triacetoxyborohydride(0.71 g, 0.34 mmol). The reaction mixture was stirred for 2 h, washedwith aqueous sat. NaHCO₃ (100 mL) and dried over MgSO₄. After filtrationand evaporation the residue was further purified by silica columnchromatography eluting with 5-10% methanol/dichloromethane to give thedesired product(4bS,8aR,9R)-11-(cyclobutylmethyl)-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carbonitrileas a yellow oil (0.48 g, 56% pure LCMS); [M+H]⁺ 379.3. This was used inthe next reaction without further purification.

Synthesis of(4bS,8aR,9R)-11-(cyclobutylmethyl)-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carboxamide

To(4bS,8aR,9R)-11-(cyclobutylmethyl)-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carbonitrile(0.48 g, 1.3 mmol) in dimethylsulfoxide (12 mL) was added potassiumcarbonate (0.53 g, 3.8 mmol). The reaction was cooled to 15° C. andhydrogen peroxide (2.0 mL, 35% aqueous solution) added dropwisemaintaining the temperature between 15 and 20° C. After addition wascomplete, the reaction was allowed to warm to room temperature. Thereaction was cooled to 0° C., quenched with water and extracted withethyl acetate. The reaction was basified with sodium hydrogen carbonatesolution and extracted with ethyl acetate (×3). The organics werecombined, washed with water (×3), brine, dried over MgSO₄ andconcentrated under reduced pressure. The product was purified by silicachromatography eluted with a gradient from 10% methanol indichloromethane to 5% NH₃/methanol in dichloromethane to give(4bS,8aR,9R)-11-(cyclobutylmethyl)-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carboxamide(0.27 g, 94% pure LCMS, 54% yield over two steps); [M+H]⁺ 397.3.

Synthesis of(4bS,8aR,9R)-11-(cyclobutylmethyl)-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamidehydrochloride

To(4bS,8aR,9R)-11-(cyclobutylmethyl)-5,7,8,8a,9,10-hexahydrospiro[9,4b-(epiminoethano)phenanthrene-6,2′-[1,3]dioxolane]-3-carboxamide(274 mg, 0.69 mmol) was added 6M HCl (aq) (12 mL). The reaction wasstirred for 24 hours until complete. The reaction was poured ontoice/NH_(3(aq)) and extracted with dichloromethane (×3). Thedichloromethane phases were combined, washed with brine, dried overMgSO₄ and concentrated under reduced pressure. The residue was purifiedby silica chromatography eluted with 5-10% NH₃/methanol indichloromethane to give(4bS,8aR,9R)-11-(cyclobutylmethyl)-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(225 mg, 99.2% pure LCMS, 93% yield).

To(4bS,8aR,9R)-11-(cyclobutylmethyl)-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(225 mg, 0.64 mmol) in ethyl acetate (10 mL) was added 2M HCl in diethylether (0.35 mL, 0.70 mmol). The product precipitated from solution andthe liquors were concentrated under vacuum. The solid was trituratedwith diethyl ether before drying under vacuum. The product was dissolvedin water and freeze dried to give(4bS,8aR,9R)-11-(cyclobutylmethyl)-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamidehydrochloride (237 mg, 99.3% LCMS, 89% yield); [M+H]⁺ 353.2. ¹H NMR (300MHz, D₂O) 7.69 (1H, s), 7.59 (1H, dd), 7.29 (1H, d), 3.84 (1H, s),2.48-3.55 (11H, m), 1.31-2.31 (11H, m).

A9. Experimental Procedure for: Synthesis of(4bS,6S,8aR,9R)-11-(cyclobutylmethyl)-6-hydroxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamidehydrochloride

To a solution of(4bS,8aR,9R)-11-(cyclobutylmethyl)-6-oxo-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(84 mg, 0.24 mmol) in methanol (4 mL) was added sodium borohydride (18mg, 0.48 mmol) at room temperature. The reaction was stirred for an hourbefore quenching with ammonium chloride solution. The aqueous phase wasbasified with 2M NaOH solution and extracted with dichloromethane (×4).The dichloromethane phases were combined, washed with brine, dried overMgSO₄ and concentrated under reduced pressure. The residue was purifiedby silica chromatography eluted with 10% NH₃/methanol in dichloromethaneto separate the diastereoisomers. The major diastereoisomer was thedesired(4bS,6S,8aR,9R)-11-(cyclobutylmethyl)-6-hydroxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(50 mg, 98.1% pure LCMS, 59% yield).

To(4bS,6S,8aR,9R)-11-(cyclobutylmethyl)-6-hydroxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamide(50 mg, 0.14 mmol) in ethyl acetate (4 mL) was added 2M HCl in diethylether (0.07 mL, 0.70 mmol). The solvent was removed under vacuum beforefreeze drying from water to give(4bS,6S,8aR,9R)-11-(cyclobutylmethyl)-6-hydroxy-6,7,8,8a,9,10-hexahydro-5H-9,4b-(epiminoethano)phenanthrene-3-carboxamidehydrochloride (55 mg, 99.0% pure LCMS, 100% yield); [M+H]⁺ 355.3. ¹H NMR(300 MHz, D₂O) 7.76 (1H, s), 7.44 (1H, d), 7.16 (1H, d), 4.02 (1H, s),3.58 (1H, s), 2.88-3.44 (5H, m), 2.70 (1H, d), 2.55 (1H, m), 2.35 (1H,dt), 0.99-2.16 (14H, m).

Part B. Biological Assays B1. In Vitro Characterization

The in vitro kinetic and pharmacological characteristics of thecompounds set forth in Table B and Table C were tested using thefollowing assays.

Opioid Receptor Binding Assay

The K_(i) (binding affinity) for opioid receptors was determined using acompetitive displacement assay as previously described in Neumeyer(Journal of Med. Chem. 2012, p3878), which is incorporated herein in itsentirety. Briefly, membrane protein from CHO (Chinese Hamster Ovarian)cells that stably expressed the cloned human opioid receptor wereincubated with 12 different concentrations of the compound set forthherein in the presence of 0.25 nM [3H]DAMGO (see Tiberi et al., Can. J.Physiol. Pharmacol. 1988, Vol. 66, p1368, which is incorporated byreference herein in its entirety) in a final volume of 1 mL of 50 mMTris-HCl, pH 7.5 at 25° C. Incubation times of 60 min were used for[3H]DAMGO (see Gulati et al., Life Sci. 1990, Vol. 47, p159, which isincorporated by reference herein in its entirety). Nonspecific bindingwas measured by inclusion of 10 M naloxone. The binding was terminatedby filtering the samples through Schleicher & Schuell No. 32 glass fiberfilters using a Brandel 48-well cell harvester. The filters weresubsequently washed three times with 3 mL of cold 50 mM Tris-HCl, pH7.5, and were counted in 2 mL Ecoscint A scintillation fluid. IC50values were calculated by least squares fit to a logarithm-probitanalysis. Ki values of unlabelled compounds were calculated from theequation Ki=(IC50)/1+S where S=(concentration of radioligand)/(Kd ofradioligand) (Cheng and Prusoff, 1973). The calculated IC50 and Kivalues for the compounds tested are set forth in Table B and Table C,herein.

Functional Assay (GTPγS Binding)

The EC50 and Imax for opioid receptors was determined using a [³⁵S]GTPγSbinding assay. This assay measures the functional properties of acompound by quantifying the level of G-protein activation followingagonist binding in studies using stably transfected cells, and isconsidered to be a measure of the efficacy of a compound. Membranes fromCHO (Chinese Hamster Ovary) cells that stably expressed the cloned humanMu opioid receptor were used in the experiments. Specifically, in afinal volume of 0.5 mL, 12 different concentrations of each testcompound were incubated with 7.5 g of CHO cell membranes that stablyexpressed the human μ opioid receptor. The assay buffer consisted of 50mM Tris-HCl, pH 7.4, 3 mM MgCl2, 0.2 mM EGTA, 3 M GDP, and 100 mM NaCl.The final concentration of [35S]GTPγS was 0.080 nM. Nonspecific bindingwas measured by inclusion of 10 μM GTPγS. Binding was initiated by theaddition of the membranes. After an incubation of 60 min at 30° C., thesamples were filtered through Schleicher & Schuell No. 32 glass fiberfilters. The filters were washed three times with cold 50 mM Tris-HCl,pH 7.5, and were counted in 2 mL of Ecoscint scintillation fluid. Dataare the mean Emax and EC50 values±S.E.M. For calculation of the Emaxvalues, the basal [35S]GTPγS binding was set at 0%, and the 100%[35S]GTPγS binding level was set at the maximum binding achieved withDAMGO. To determine antagonist activity of a compound at the μ opioidreceptors, CHO membranes expressing the t opioid receptor, wereincubated with 12 different concentrations of the compound in thepresence of 200 nM of the μ agonist DAMGO. The Emax values are themaximal percentage increase of [35S]GTPγS binding induced by a testcompound relative to basal [35S]GTPγS binding in the absence of anydrug. Data for antagonists are the mean Imax and IC50 values±S.E.M. Thecalculated EC50 and Imax values for the compounds tested are set forthin Table B and Table C, herein. It should be noted that the GTPγSbinding assay described above is performed under conditions such thatthe observed Emax value for buprenorphine in this assay is at least 50%compared to baseline.

TABLE B Structure mu_Ki mu_EC50 mu_Emax mu_IC50 mu_Imax

 0.98   34 ± 17 26  87 ± 13   74 ± 3

 0.079    0.56 25     2.2 68

 0.19    3.3 27    28 66

 0.43    0.35 64     0.28 30

18    50 29    970 67 @ 10 uM

 0.061    1.1 28     0.71 67

 0.54    20 47    130 47

 2.7    61 38    280 64

 0.08    1.3 24    10 74

22 >630 56 NI NI

32 >600 59 16% @ 10 uM

 0.49    16 56    74 42

 0.2    0.19 56     0.18 53

 0.061    0.075 34     0.079 59

 0.77    1.8 38     1.6 57

 0.16   1 ± 0.11 31 ± 1 2.2 ± 0.5   69 ± 1.5

 0.28  1.4 ± 0.06 30 ± 2.2 4.2 ± 0.6   71 ± 0.8

 0.11  1.1 ± 0.3 29 ± 1 2.0 ± 0.3   74 ± 2

0.59 ± 0.07  2.8 ± 0.3 18 ± 1    47 78.5 ± 4.5

0.10 ± 0.04 0.98 ± 0.12 18 ± 5     3.8   80 ± 1

 0.097    0.53 28     1.3 65

 0.22    3.3 33    14 69

 0.097    0.39 42     1.1 54

 0.12    2.1 38     5 63

 0.13    1.5 44     3.7 66

 0.56    4.2 49    34 54

 0.5    15 35    51 70

 0.19    2.3 36    14 55

 0.1    3.5 32     3.3 73

22    60 27    950 65

 1.2    12 35    69 65

 0.82    13 26    85 76

 4.6    84 23    210 74

 2.1   110 (12) 43 (7) >1300 (280) 53% @ 10 uM

 0.11    4.8 53    26 37

 0.2    0.59 51     0.84 57

 0.26    0.85 48     3.5 53

 0.3    1.4 48     1.1 56

 0.68    22 25    47 83

 0.17    2.6 19     5.2 79

 0.27    5.2 32    18 59

 0.37    2.9 46     1.5 43

 2.3    62 18    170 87

 3    41 19    170 83

23   190 35 >3000 57 @ 10 uM

 4.4    20 20    340 76

 1.2  1.6    44 85

TABLE C μ μ μ μ μ Compound Ki/nm EC50/nM Emax/% IC50/nM Imax/%

0.083 1.3 18  1.7 82

0.14 11  0.65 86

5.8 —  7.7 43 91

1.2 — 11 38 86

0.12 2.2 46 14 41

0.098 2.5 54  7.8 59

0.1 0.89 21  1.5 80

0.05 20 58 89 morphine 0.32   34 ± 14 96.5 ± 36 No No inhibitioninhibition nalbuphine 1.3 ± 0.4   21 ± 15   26 ± 1.55   88 ± 18 74 ± 2buprenorphine 0.41 0.30 ± 0.042   53 ± 2.3 0.45 ± 0.060 48 ± 1.7

B2. Thermal Pain Assay

The antinociceptive effect of the compounds disclosed herein isdetermined using a rodent hot plate model. This model tests theresponses to acute thermal pain in rats as set forth below.

Male Sprague-Dawley rats (275-425 g) are used for all studies. Rats arehoused 2/cage and are given food and water ad libitum. Body weights weretaken once before testing begins and rats were marked on their tail toindicate numbering. The hot plate apparatus (Columbus Instruments) wasused to measure antinociception to acute thermal pain.

Rats are placed individually on the hot plate apparatus (surfacetemperature is equal to 52.5° C. and is confirmed with an infraredthermometer at the beginning of each study) and the response latency tolick either hind paw is recorded. The maximum response latency (MRL) isset to 60 seconds to avoid potential thermal injury associated withlonger exposure times. Rats are tested for a baseline hot plate response(licking one hind paw) immediately prior to subcutaneous injection withtest compound. Any rat which displays a baseline response latencygreater than 30 seconds is removed from the study. The latency to lick ahind paw is compared to the dose of morphine (7.5 mg/kg, SC) thatproduced a maximum response latency of 60 seconds when measured 30minutes after administration. Following test compound administration,rats are tested 30, 60, 90, 120, and 240 minutes later on the hot plate.The time to lick one hind paw is recorded as the response latency foreach rat.

Raw data is reported as the time (in seconds) to lick one hind pawfollowing exposure to the hot plate. The mean and SEM of the responseslatencies for each experimental group are calculated and a line graphdepicting mean hot plate latency vs. time is generated using GraphPadPrism. An increase in mean response latency above baseline followingtest compound administration is indicative of an antinociceptive effect.

In one study, the antinociceptive effects of Compound A, either alone orin combination with morphine were determined using the hot plate assaydescribed above. Specifically, rats were administered: 1) 5 mg/kgmorphine; 2) 1 mg/kg Compound A; 3) 5 mg/kg morphine and 0.01 mg/kgCompound A; 4) 5 mg/kg morphine and 0.1 mg/kg Compound A; or 5) 5 mg/kgmorphine and 1 mg/kg Compound A. The results, set forth in FIG. 1, showthat although Compound A inhibits morphine analgesia at doses rangingfrom 0.01 mg/kg to 1 mg/kg, Compound A alone has no antinociceptiveeffect at a dose of 1 mg/kg.

In another study, the antinociceptive effects of Compound A andbuprenorphine were compared using the hot plate assay described above.Specifically, rats were administered with either 10 mg/kg of Compound A,or 1 mg/kg of buprenorphine. The results, set forth in FIG. 2, show thatbuprenorphine inhibits thermal pain in rats at a dose of 1 mg/kg,whereas Compound A has no antinociceptive effect at a dose of 10 mg/kg.

In another study, the antinociceptive effects of morphine, and CompoundsB, C, D, and E, separately, were determined using the hot plate assaydescribed above. Specifically, rats were administered: 1) 7.5 mg/kgmorphine; 2) 10.0 mg/kg Compound B; 3) 10.0 mg/kg Compound C; 4) 10.0mg/kg Compound D; or 5) 10.0 mg/kg Compound E. The results, set forth inFIG. 4, show that morphine inhibits thermal pain at a dose of 7.5 mg/kg,and that Compounds B, C, D, or E have no antinociceptive effect at adose of 10.0 mg/kg.

B3. In Vivo Dopamine Efflux Assay

The neurochemical response of the compounds disclosed herein isdetermined by in vivo microdialysis in awake rats. Intra-cranialmicrodialysis in rats allows the sampling of extracellular cerebrospinalfluid (CSF) from specific brain regions of interest and the measurementand quantitation of neurotransmitter, neuropeptide, and drugconcentrations following the analysis of sampled dialysate withbioanalytical chemistry techniques. This technique allows measurementand comparison of neurotransmitter release in response to test compoundsto basal neurotransmitter levels. The nucleus accumbens shell is a brainregion which is critically important for understanding the rewardingeffects of a variety of stimuli including food, mating behavior anddrugs of abuse. Rewarding stimuli have been shown to act though multiplepathways to modulate the mesolimbic dopamine system, ultimatelyresulting in acute increases in extracellular DA (DA_(ext)) within thenucleus accumbens shell following systemic administration orself-administration. In these studies, microdialysate collected fromprobes implanted in the NAc-sh is analyzed for dopamine content by HPLCcoupled to electrochemical detection (HPLC-EC) as set forth below.

Male Wistar rats (275-425 g) are used for all studies. Rats were housed2/cage and are given food and water ad libitum. Approximately 3-4 daysafter arrival to the animal facility, rats underwent surgicalimplantation of microdialysis guide cannula to guide insertion of themicrodialysis probe. Rats are anesthetized with a mixture ofketamine/xylazine (80/6 mg/kg IP) and placed in a stereotaxic apparatus.Ophthalmic lubricating petroleum based ointment is applied to the eyesas needed. The surgical area is shaved and prepared with a betadinescrub and wiped with alcohol. The skull is exposed and small burr holeswere drilled to allow for the guide cannula to pass through and for themounting screws to be attached to the skull. Guide cannula (CMA-12,CMA-Microdialysis, SWE) are stereotaxically implanted towards the NAc-sh(final microdialysis coordinates relative to bregma: A/P+1.70; M/L±0.80;D/V −5.90 from the top of the skull) (Paxinos and Watson, “The RatBrain”, 6^(th) Edition, 2008). Each guide cannula is secured with 3, ⅛″skull screws (Small Parts Inc, USA) and cranioplastic cement (GC FujiPlus Capsule; Henry Schein, USA). Following 3-4 days of recovery,microdialysis probes (CMA-12, CMA-Microdialysis, SWE) with a 2 mm activemembrane length are inserted through the guide cannula and rats areindividually tethered to a CMA 120 microdialysis system(CMA-Microdialysis, SWE). Rats are continuously perfused overnight withsterile artificial cerebrospinal fluid (aCSF) (CMA CNS PerfusionSolution; CMA-Microdialysis, SWE) via a syringe pump at 0.2 μl/minute.The following morning, continuous perfusion of aCSF was increased to 2.0μl/minute and the flow rate was equilibrated for at least 2 hours priorto experimentation.

Microdialysis occurred on the day following probe insertion.Microdialysis samples are collected automatically at 15 minute intervalsvia a chilled microfraction collector for a total of 6.0 hours.Following equilibration, a 1.5 hour baseline measurement (6 fractions)of neurotransmitter levels is collected. Following baselinemeasurements, rats are separately administered various concentrations oftest compound. Fractions were analyzed via HPLC-EC to determine dopamineconcentrations.

Microdialysis fractions are analyzed via HPLC-EC using an AlexysMonoamine Analyzer (Antec Leyden, NLD) or via UHPLC-EC using an AlexysNeurotransmitter Analyzer. For HPLC-EC detection, an aliquot of eachfraction (10 ul) is injected onto a 1 μm reverse-phase C18 column(HSS-T3, Waters Corp., Milford, Mass.). DA is eluted using a mobilephase (pH 6.0) consisting of 50 mM phosphoric acid, 8 mM KCL, 0.1 mMEDTA, 6.5% acetonitrile, and 1200 mg/L octane sulfonic acid. DA isdetected using a Decade II amperometric detector (Antec Leyden) with aglassy carbon electrode maintained at approximately 0.460V relative to asalt-bridge reference electrode. For UHPLC-EC detection, an aliquot ofeach fraction (10 ul) is injected onto a 1 μm reverse-phase C18 column(HSS T3, Waters Corp., Milford, Mass.). DA is eluted using a mobilephase (pH 4.00) consisting of 50 mM phosphoric acid, 8 mM KCL, 50 mMCitric Acid, 0.1 mM EDTA, 6.5% acetonitrile, and 600 mg/L octanesulfonic acid. DA is detected using a Decade II amperometric detector(Antec Leyden) with a glassy carbon electrode maintained atapproximately 0.55V relative to a Ag/AgCl reference electrode.

All data is recorded and analyte levels quantitated using a Clarity 3.0software package (Data Apex, Czech Republic). A 6-point standard curve(0.25, 0.5, 1.0, 2.0, 4.0 and 8.0 pg DA/10 μl injection) is run dailyprior to neurotransmitter analysis. The standard curve is fittedlinearly and neurotransmitter content in microdialysate samples isquantitated based on the corresponding standard curve. The amount ofdopamine or metabolites is quantified as “on-column” in picograms ofanalyte per 10 μl sample injection onto the column. Raw data arereported as picograms of dopamine per 10 μl sample and transformed(using Graph Pad Prism 5.0) to percentage of pre-drug baseline for eachanimal, as defined as the average of the six baseline microdialysissamples. Percentage change from baseline vs. time is then graphed usingGraphPad Prism 5.0. Following completion of the study, all animals areanalyzed via histological methods to ensure proper probe placement withthe nucleus accumbens shell. Those animals with probe placement outsideof the nucleus accumbens shell are excluded from the final data analysis

To verify probe placement, rats are euthanized with an IP injection of50% Euthasol (Virbac, AH Inc, Fort Worth, Tex.) shortly aftermicrodialysis. Brains are rapidly dissected and frozen on dry ice andstored at −80° C. Coronal sections (approximately 60-μm) are then slicedat the level of the nucleus accumbens and digitally photographed forarchival purposes. Only data from animals with verified probe placementare included in data analysis.

In one study, the amount of dopamine release induced by Compound A andbuprenorphine in the rat nucleus accumbens was determined using themicrodialysis assay herein. Specifically, rats were separatelyadministered with Compound A (at 0.01 mg/kg, 0.1 mg/kg, or 1 mg/kg) orbuprenorphine (at 0.001 mg/kg, 0.003 mg/kg, 0.01 mg/kg, 0.1 mg/kg, or 1mg/kg) and microdialysate was sampled for 4.5 hours (18 fractions). Theresults of these experiments are set forth in FIG. 3. These data showthat Compound A induced a dose dependent increase in dopamine efflux inthe rat nucleus accumbens, achieving a maximum dopamine efflux of about300% over baseline at 0.1 mg/kg of Compound A. Buprenorphine alsoinduced a dose dependent increase in dopamine efflux. Although, nomaximum dopamine efflux level for buprenorphine was determined, themaximum dopamine efflux induced by buprenorphine is clearly much greaterthan that obtainable using Compound A. The lower ceiling level ofdopamine efflux of exhibited by Compound A relative to buprenorphineindicates that Compound A will likely have a lower risk of opioiddependence, opioid addiction and/or opioid withdrawal symptoms comparedto buprenorphine.

In other studies, the amount of dopamine release induced by Compounds B,C, D, and E in the rat nucleus accumbens was determined using themicrodialysis assay herein. Specifically, rats were administered (viasubcutaneous injection at T=0) separately with Compounds B, C, D, or Eat doses of 0.1 mg/kg, 1 mg/kg, or 10 mg/kg, and microdialysate wascontinuously sampled for 4.5 hours. The results of these experiments areset forth in FIGS. 5-8. Compound B exhibited a maximum dopamine effluxof about 150% to about 200% over baseline at a dose of 10 mg/kg.Compound C exhibited a maximum dopamine efflux of about 125% to about200% over baseline at the three dose levels. Compounds D and E exhibiteda maximum dopamine efflux of about 125% to about 250% over baseline atthe three dose levels. These low ceiling levels of dopamine effluxindicate that Compounds B, C, D, and E will likely have a lower risk ofopioid dependence, opioid addiction and/or opioid withdrawal symptoms.

B4. In Vivo Forced Swim Test

The Forced Swim Test is a classical preclinical model used to assessantidepressant effects of test compounds in rats. Rats forced to swim inan inescapable cylinder adopt a characteristic immobile posture after aperiod of vigorous swimming. Immobility has been shown to be reduced bymost clinically effective antidepressant drugs. Furthermore, thisparadigm has the benefit of being able to distinguish potentialantidepressant compounds from other behavioral paradigms that measureactivities (open-field) or other compounds that might havedose-dependent effects on general locomotor activities unrelated tomood.

A male, Wistar-Kyoto rat is placed into its assigned clear Plexiglascylinders of water (23-25° C.) for a 15-min pretest swim. A compound isthen administered in the rat by subcutaneously (sub-Q) injectionsfollowing a dosing schedule. The sub-Q dosing schedule includes oneinjection at 0.5 hr after the pretest swim, one injection at 5 hrsbefore a test swim, and one injection at 1 hr before the test swim. Eachtest swim lasts 6 minutes, and this test swim is carried out within 24hours after the pretest swim. The test swim is recorded using a digitalvideo recording system and subsequently analyzed manually for immobilitybehavior.

In one study, reductions of the duration of immobility in rats inducedby different doses of Compounds A, B and C were determined using theForced Swim Test herein. Specifically, rats were administered with avehicle (saline), Compound A, Compound B, or Compound C at a dose rangebetween 0 and 10 mg/kg, and durations of immobility were recorded. Theresults of these experiments are set forth in FIG. 9. Maximal effects ofCompounds A, B and C in the Forced Swim Test are shown in FIGS. 9( a),9(b) and 9(c), respectively. Compounds A, B and C significantly (p<0.05)decreased immobility time in the Forced Swim Test compared to salinetreated controls. The reductions of immobility indicate that CompoundsA, B and C will likely improve depressive-like behavior.

EQUIVALENTS

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, many equivalents to the specificembodiments and methods described herein. Such equivalents are intendedto be encompassed by the scope of the following claims.

INCORPORATION BY REFERENCE

The entire contents of all patents, published patent applications andother references cited herein are hereby expressly incorporated hereinin their entireties by reference.

1. A method of treating a depressive symptom in a subject comprisingadministering to the subject a compound of Formula I:

or a pharmaceutically acceptable salt thereof, wherein R₁ is cyclobutyl,

R₂ is H, hydroxyl, or methoxy; and R₃ and R₄ are each, independently, H,hydroxyl, or NR₅R₆, wherein R₅ and R₆ are each independently H, alkyl oroptionally substituted acyl, or alternatively, R₃ and R₄, together withthe carbon atom to which they are attached, form C═O or C═CH₂.
 2. Themethod according to claim 1, wherein the compound of Formula I is:

or a pharmaceutically acceptable salt thereof.
 3. The method of claim18, wherein the opioid receptor agonist is a compound of Formula II:

or a pharmaceutically acceptable salt thereof, wherein R₁ is C₁-C₆alkyl, C₂-C₆ alkenyl, cycloalkyl, heterocyclyl, hydroxyalkyl, oralkoxyalkyl; R_(1a) is H or methyl; R₂ and R₃ are each methyl, oralternatively, R₂ and R₃, together with the carbon atoms to which theyare attached, form a 6-membered unsubstituted carbocyclic ring; when

is a single bond, R₄ is H; and when

is a double bond, R₄ is O.
 4. The method according to claim 3, whereinthe compound of Formula II is:

or a pharmaceutically acceptable salt thereof.
 5. The method of claim18, wherein the μ opioid receptor agonist is a compound of Formula III:

or a pharmaceutically acceptable salt thereof, wherein R₁ is C₁-C₆alkyl, C₂-C₆ alkenyl, aryl, cycloalkyl, heterocyclyl, benzyl,hydroxyalkyl, or alkoxyalkyl; R_(1a) is H or methyl; R₂ and R₃ are eachH, methyl, or ethyl, or alternatively, R₂ and R₃, together with thecarbon atoms to which they are attached, form a 6-membered unsubstitutedcarbocyclic ring or carbonyl-substituted carbocyclic ring; R₄ and R₅ areeach, independently, H, hydroxyl, or C₁-C₆ alkyl; R₆ is unsubstituted orsubstituted C₆-C₁₀ aryl, or substituted or unsubstituted heteroarylcomprising one or two 5- or 6-membered rings and 1-4 heteroatomsselected from N, O and S; and R₇ and R₈ are each, independently, H orhydroxyl.
 6. The method according to claim 5, wherein the compound ofFormula III is:

or a pharmaceutically acceptable salt thereof.
 7. The method of claim18, wherein the opioid receptor agonist is a compound of Formula IV:

or a pharmaceutically acceptable salt thereof, wherein R₁ is C₁-C₆alkyl, C₂-C₆ alkenyl, aryl, cycloalkyl, heterocyclyl, benzyl,hydroxyalkyl, or alkoxyalkyl; R_(1a) is H or methyl; R₂ is H, hydroxyl,or methoxy; and R₃ and R₄ are each methyl, or alternatively, R₃ and R₄,together with the carbon atoms to which they are attached, form a6-membered unsubstituted carbocyclic ring.
 8. The method according toclaim 7, wherein the compound of Formula IV is:

or a pharmaceutically acceptable salt thereof.
 9. A method of treating adepressive symptom in a subject comprising administering to the subjecta compound selected from:

or a pharmaceutically acceptable salt thereof.
 10. The method of claim1, wherein the compound is a μ opioid receptor agonist that exhibits anEmax of 5% to 45% in a GTPγS binding assay.
 11. The method of claim 10,wherein the Emax is 15% to 35% in a GTPγS binding assay.
 12. The methodof claim 10, wherein said agonist has a low risk of opioid dependence,opioid addiction, and/or symptoms of opioid withdrawal.
 13. The methodof claim 1, wherein the compound exhibits a maximal dopamine efflux inthe nucleus accumbens of 125% to 300% over base line in a rat. 14.(canceled)
 15. The method of claim 1, wherein the compound does notattenuate thermal pain in a rodent hot plate model when administered ata dose of at least 1 mg/kg.
 16. (canceled)
 17. (canceled)
 18. A methodof treating a depressive symptom in a subject in need thereof, themethod comprising administering to the subject an effective amount of aμ opioid receptor agonist that exhibits an Emax of 5% to 45% in a GTPγSbinding assay.
 19. (canceled)
 20. (canceled)
 21. A method of treating adepressive symptom in a subject in need thereof, the method comprisingadministering to the subject an effective amount of a compound thatexhibits a maximal dopamine efflux in the nucleus accumbens of 125% to300% over base line in a rat.
 22. (canceled)
 23. A method of treating adepressive symptom in a subject in need thereof, the method comprisingadministering to the subject an effective amount of a compound that doesnot attenuate thermal pain in a rodent hot plate model when administeredat a dose of at least 1 mg/kg.
 24. (canceled)
 25. (canceled) 26.(canceled)
 27. The method of claim 18, wherein the depressive symptom isdepressed mood, loss of pleasure, loss of appetite, sleep disturbance,psychomotor changes, fatigue, and/or post-partum depression. 28.(canceled)
 29. The method of claim 18, wherein the depressive symptom isacute stress disorder, adjustment disorders with depressed mood,Asperger syndrome, attention deficit, bereavement, bipolar I disorder,bipolar II disorder, borderline and personality disorder, cyclothymiaand dysthymia, depression such as major depressive disorder (MDD) andtreatment-resistant disorder (TRD), Dysthymic disorder, hyperactivitydisorder, impulse control disorder, mixed mania, obsessive-compulsivepersonality disorder (OCD), paranoid, post-traumatic stress disorder,seasonal affective disorder, self-injury separation, sleep disorder,substance-induced mood disorder, Tourette syndrome and tic disorder,and/or Trichotillomania.
 30. The method of claim 18, wherein thedepressive symptom is an anxiety disorder, wherein the anxiety disorderis generalized anxiety disorder, panic, agoraphobia, acute stress,and/or post-traumatic stress disorder.
 31. (canceled)